The Community Market enables users to trade with each other using funds in their Steam Wallets.
Marketable items include supply crates, paints and keys and can be purchased from inventories or the Steam Marketplace.
Steam will deduct a 5% fee from the buyer to cover development costs and to protect against fraud. Each game, meanwhile, will have its own specific fees, with Team Fortress 2 items subject to a 10% charge.
"With over a half million trades made every week, the trading system has been very successful," explained Valve's Tony Paloma.
"Extending game economies beyond trades and giving players a way to turn gameplay into funds for new items and games is a key component for moving that success forward," he added.
The Steam Community Market will be available to other titles in the New Year.
Steam recently made its Big Picture mode available to all users in an update.
The feature introduces a reformatted full-screen option for the Steam client that users can easily navigate with a controller on a television screen.
Watch the Big Picture mode trailer below: