Need to add dependable RS-232 connectivity to a modern desktop or workstation? A PCIe serial port expansion card is still the easiest way to support legacy hardware without relying on flaky USB adapters.
Below, we focus on practical options for everything from a single COM port to multi-port setups for industrial, lab, and point-of-sale environments.
Best 10 PCIe Serial Port Expansion Card Picks for 2026
Top Pick
StarTech 2-Port Low Profile RS232 Serial Adapter
- 2 RS232 DB9 ports with 16950 UART
- Configurable 12V, 5V, or no power on pin 9
- Includes low-profile and full-profile brackets
Best For: Flexible 2-port installs in desktops, servers, and industrial systems
High-Density Choice
IO CREST 8-Port PCIe RS-232 Serial Card
- Eight independent RS232 DB9 ports
- PCIe 2.0 x1 with up to 25 Mbps data rate
- Works with Windows, macOS, and Linux
Best For: Large serial-device setups that need maximum port count
Value Upgrade
StarTech 2-Port PCIe Serial Card with 16C1050 UART
- Two DB9 ports with up to 460Kbps transfer
- Fits 1x to 16x PCIe slots
- Includes standard and low-profile brackets
Best For: Windows-based upgrades that need simple dual-port RS232 connectivity
Budget Dual-Port
XRIKUI PCIe RS-232 DB9 Serial Card
- Two RS232 DB9 ports with AX99100 chipset
- Fits PCIe x1, x4, x8, and x16 slots
- Includes full-size and low-profile brackets
Best For: Older Windows and Linux systems that need basic dual-port serial expansion
Dual DB9 Expansion for Standard PCs
ASIX AX99100 2-Port PCIe RS232 Card
- Adds 2 RS232 DB9 ports via PCIe x1
- ASIX AX99100 with 256-byte FIFO
- Works with Windows Vista-11 and Linux
Best For: Users adding two reliable serial ports to PCs or industrial gear
Budget 2-Port COM Upgrade
WCH382 Low-Bracket PCIe Serial Card
- 2 DB9 ports with up to 230400 Bps
- Plug and Play with IRQ and IO auto-select
- Low bracket included for compact cases
Best For: People needing an affordable dual-port RS232 add-in card
Premium 4-Port Serial Hub
StarTech PEX4S953 4-Port PCIe RS232
- Adds 4 configurable DB9 RS232 ports
- Up to 921.6 Kbps per port
- Includes standard and low-profile brackets
Best For: Users who need four serial ports with configurable pin 9 power
Dual-Port Serial Expansion
- Adds 2 RS-232 DB9 ports from one PCIe x1 slot
- Includes full-size and low-profile brackets
- Supports Windows XP through 11 and Linux
Best For: dual-device serial setups in desktop or slim PCs
Compact Single-Port Serial
- One RS-232 DB9 port with 16950 UART
- Optional 5V, 12V, or no power on pin 9
- Low-profile bracket installed with full bracket included
Best For: single-port installs in POS, PLC, and lab systems
Feature-Rich Single Port
- 16C1050 UART with LED status lights
- COM retention plus 5V/12V pin 9 power
- Low-profile bracket included for compact builds
Best For: IT and industrial setups needing a single reliable RS-232 port
Top Pick – StarTech 2-Port Low Profile RS232 Serial Adapter
If you need a dependable PCIe serial port expansion card for industrial gear, point-of-sale systems, or lab equipment, this 2-port StarTech model is built around a 16950 UART and ASIX AX99100 solution. It offers two DB9 RS232 ports with configurable pin 9 power options and comes ready for both standard and low-profile installs.
Best For: Users who want a flexible 2-port PCIe serial card for mixed desktop and server installations.
Pros:
- Two independent DB9 RS232 ports with up to 921.6Kbps per port
- Configurable pin 9 power output: 12V, 5V, or none
- Includes both low-profile and full-profile brackets
- Works with Windows and Linux
Cons:
- Only adds two serial ports, so it may not suit larger multi-device setups
- Designed for RS232 devices specifically, not broader interface types
This is a strong all-around choice if you want a PCIe serial expansion card with practical hardware options and wide deployment flexibility. The configurable power on pin 9 is especially useful for connected devices that need it.
High-Density Choice – IO CREST 8-Port PCIe RS-232 Serial Card
8 Port RS-232 DB9 Serial PCI-e 2.0 x1 Card XR17V358 Chipset 16C550 UART SI-PEX15041
Check Price On AmazonWhen a PCIe serial port expansion card needs to connect a lot of equipment, this 8-port IO CREST model stands out. It supports eight independent RS232 ports, uses an XR17V358 chipset with 256-byte TX/RX FIFOs, and is built for PCIe 2.0 x1 slots with broad operating system support.
Best For: Multi-device setups that need eight RS-232 connections from one PCIe card.
Pros:
- Eight independent 9-pin RS232 serial ports
- Up to 25 Mbps serial data rate
- Includes fan-out cable, driver CD, and user manual
- Supports Windows, macOS, and Linux
Cons:
- Uses an 8-port fan-out cable, which adds more cable management
- More card capacity than many simple single-device installs need
If port count matters most, this is the most expansion-friendly option in the group. The wide OS support and included accessories make it a practical fit for industrial machines, printers, and other serial-heavy setups.
Value Upgrade – StarTech 2-Port PCIe Serial Card with 16C1050 UART
This PCIe serial port expansion card is a straightforward dual-port RS232 solution for users who want broad slot compatibility and simple installation. It supports 1x through 16x PCI Express slots, includes plug-and-play support with IRQ sharing, and is positioned for common upgrade use cases like manufacturing, POS, and security devices.
Best For: Users who need a simple 2-port PCIe serial upgrade for Windows systems.
Pros:
- Compatible with a wide range of PCIe slot sizes
- Two DB9 serial ports with up to 460Kbps data transfer
- Includes standard and low-profile bracket options
- Plug-and-play installation with IRQ sharing
Cons:
- Windows support is the primary operating system listed
- Lower maximum transfer rate than some higher-end alternatives
For buyers who want a familiar dual-port serial card without extra complexity, this model keeps the focus on compatibility and ease of setup. It makes the most sense when you need reliable RS232 connectivity rather than higher port density.
Budget Dual-Port – XRIKUI PCIe RS-232 DB9 Serial Card
For buyers looking for a practical PCIe serial port expansion card for older Windows PCs or Linux systems, this dual-port XRIKUI card covers the basics well. It uses the ASIX AX99100 solution with 256-byte FIFO transfer, supports PCIe x1 and larger slots, and includes both full-size and low-profile brackets.
Best For: Budget-minded users adding two RS-232 DB9 ports to compatible desktop or industrial systems.
Pros:
- Two independent RS232 serial ports
- Compatible with Windows XP through 11 and Linux kernels 2.6.x to 5.x
- Includes full-size and low-profile brackets
- Supports PCIe x1, x4, x8, and x16 slots
Cons:
- Driver installation is required for Windows and Linux setup
- Best fit is limited to RS232 DB9 devices
This is a sensible choice if you need two serial ports and want broad legacy OS support. The bracket flexibility and slot compatibility make it easy to adapt to different PC cases.
Dual DB9 Expansion for Standard PCs – ASIX AX99100 2-Port PCIe RS232 Card
If you need a PCIe serial port expansion card for adding dependable RS232 connections to a desktop or industrial machine, this 2-port model keeps things straightforward. It adds two DB9 serial ports through a PCI Express x1 slot and is aimed at common serial-device setups like POS systems, scanners, printers, security gear, and measurement equipment.
Best For: Desktop and industrial users who want two RS232 DB9 ports with broad OS support.
Pros:
- Adds 2 RS232 DB9 ports through a PCIe x1 slot.
- Uses the ASIX AX99100 with 256-byte FIFO for efficient transfers.
- Compatible with Windows Vista through 11 and multiple Linux kernel versions.
- Full-size bracket suits standard desktop installs and ARM hardware platforms.
Cons:
- Driver installation is required for supported systems.
- Not a fit if you need more than two serial ports.
For buyers who mainly want a practical two-port serial add-in, this card covers the essentials without extra complexity. Its broad compatibility and common-device focus make it a solid choice for everyday RS232 expansion.
Budget 2-Port COM Upgrade – WCH382 Low-Bracket PCIe Serial Card
This PCIe serial port expansion card is built for users who want a simple two-port RS232 upgrade with broad OS coverage. It adds dual DB9 COM ports over a PCI-Express x1 lane and includes a low bracket, making it a practical fit for smaller cases and straightforward desktop or server setups.
Best For: Buyers wanting a basic dual-port serial upgrade with easy installation support.
Pros:
- Provides 2 fast UART serial ports with up to 230400 Bps transfer rates.
- Plug and Play design automatically selects IRQ and IO address.
- Supports IRQ sharing for flexible system integration.
- Includes a low bracket for compact installations.
Cons:
- Driver installation is needed from the included CH38XDRV file.
- It is limited to two serial ports.
This card is a sensible pick if you need the basics: two RS232 ports, broad Windows and Linux support, and a low-profile option in the box. It focuses on compatibility and convenience rather than advanced multiport features.
Premium 4-Port Serial Hub – StarTech PEX4S953 4-Port PCIe RS232
For buyers looking at a PCIe serial port expansion card with more headroom, this StarTech 4-port model is built for multi-device RS232 setups. It uses a 16950 UART based on the ASIX AX99100 and includes a DB44-to-4x DB9 breakout cable, so it suits workstations and servers that need several serial connections in one install.
Best For: Multi-device installations that need four configurable RS232 ports.
Pros:
- Provides 4 DB9 RS232 ports with speeds up to 921.6 Kbps per port.
- Each port is individually configurable for 12V, 5V, or no power on pin 9.
- Includes standard and low-profile brackets for flexible installs.
- Backed by lifetime warranty and supports Windows and Linux.
Cons:
- Uses a breakout cable, which adds a little more cabling to manage.
- More port capacity than needed for simple two-device setups.
If you need multiple serial links and want per-port flexibility, this card stands out with its four-port design and configurable power options. It is the strongest fit in this group for more demanding POS, control, and lab-style environments.
Dual-Port Serial Expansion – Dual DB9 PCIe Card
If you need a PCIe serial port expansion card for two legacy DB9 devices, this LinksTek adapter is a straightforward way to add RS-232 connectivity through an available PCI Express slot. It is built around the ASIX AX99100 solution, supports Windows XP through Windows 11 plus Linux, and includes both standard and low-profile brackets for mixed desktop setups.
Best For: users who want two RS-232 ports for POS gear, industrial equipment, scanners, or printers in a desktop or slim PC.
Pros:
- 2-port RS-232 DB9 design for connecting multiple serial devices
- Includes full-size and low-profile brackets for different case types
- Supports PCIe x1 and also fits x4, x8, and x16 slots
- Works with a wide range of Windows versions and Linux kernels
Cons:
- Windows requires driver installation
- Linux users may need to compile source code from the driver CD
- Slim PC users must swap the bracket by hand
This is a practical choice if you need two serial ports and broad platform compatibility rather than advanced extras. Its value is in simple expansion, flexible bracket support, and compatibility with common legacy serial workflows.
Compact Single-Port Serial – 1-Port Low Profile Adapter
This PCIe serial port expansion card is a solid pick when you only need one dependable RS-232 connection with flexible power options. StarTech rates it for up to 921.6Kbps, includes a low-profile bracket pre-installed, and supplies a full-profile bracket for standard cases.
Best For: single-port serial installations in point-of-sale, automation, scientific, or medical environments.
Pros:
- 1 DB9 RS-232 port with 16950 UART and 256-byte FIFO
- Optional 12V, 5V, or no power on pin 9
- Low-profile bracket installed, plus full-profile bracket included
- Supports Windows and Linux operating systems
Cons:
- Only one serial port, so it is not suited for multi-device expansion
- Designed for systems with a PCI Express slot and compatible OS
For users who need a compact, well-supported serial add-in card, this model covers the essentials without extra complexity. The bracket flexibility and configurable pin 9 power make it especially useful in mixed deployment environments.
Feature-Rich Single Port – COM Retention DB9 Card
For buyers looking for a PCIe serial port expansion card with modern serial-card features, this StarTech model adds one RS-232 DB9 port with a 16C1050 UART, COM retention, and LED status lights. It is aimed at practical legacy-device connections while keeping installation flexible with a low-profile bracket included and support for Windows and Linux.
Best For: IT and industrial users connecting barcode scanners, receipt printers, scales, PLCs, or medical devices.
Pros:
- 16C1050 UART with up to 921.6 Kbps and 256-byte FIFO
- COM retention and built-in LED status lights
- Supports 5V or 12V over pin 9
- Low-profile bracket included for compact systems
Cons:
- Single-port design limits expansion for multiple serial devices
- Linux support is listed for older 2.6.13 and older LTS versions only
This is the most feature-rich option in the group if you value status visibility and COM retention alongside standard RS-232 support. It is a strong fit for legacy workflows where dependable serial communication matters more than port count.
How We Picked the Best PCIe Serial Port Expansion Card
We prioritized PCIe Serial Port Expansion Card options that are suitable for real-world legacy device use, with an emphasis on stable chipsets, driver support, port count, and form factor compatibility. We also looked for models that make sense for mixed environments, including Windows and Linux systems, and cards that fit common desktop and server builds.
Quick Comparison
If you only need one device connection, a 1-port card is the simplest choice. Two-port models are the sweet spot for most office, retail, and lab setups. Choose a 4-port card if you want to consolidate multiple serial devices in one machine, and go with an 8-port card when you need higher-density expansion for industrial control, automation, or test benches.
Key Buying Factors for a PCIe Serial Port Expansion Card
Port Count
Start by counting your current devices and leaving room for growth. A card with more ports is not always better if you only need one or two connections, but it can simplify cable management and reduce future upgrades.
UART and Chipset Quality
Look for known UART families and controller chipsets with solid driver support. Better chipsets tend to handle communication more reliably, especially when multiple serial devices are active at once or when data timing matters.
Operating System Support
Make sure the card supports your target OS before buying, especially if you are using older industrial software or a newer Windows release. Linux compatibility can also matter for embedded and control systems.
Bracket and Physical Fit
Low-profile and full-height bracket support can be important in compact PCs, rack systems, and workstations. Check the card’s dimensions and included accessories so installation goes smoothly.
Device Compatibility
Not every serial card behaves the same with specialty hardware. If you are connecting barcode scanners, CNC equipment, lab instruments, or POS gear, confirm that the card supports the baud rates and RS-232 signaling your devices require.
Who Should Buy Which PCIe Serial Port Expansion Card?
Choose a 1-port PCIe Serial Port Expansion Card if you need one reliable legacy connection and want the smallest, simplest install. Pick a 2-port card for most users, since it offers a strong balance of price, flexibility, and compatibility. A 4-port model is a better fit for busy offices or small industrial setups that need several COM devices on one system. An 8-port card is the best choice for higher-volume environments where consolidating many serial connections into a single PC saves time, space, and maintenance effort.
In short, the best card is the one that matches your device count, operating system, and enclosure size. Focus on those basics first, and you will end up with a PCIe Serial Port Expansion Card that is easier to install and more dependable over time.