A broker that takes the contra-side (opposite side) of a deal or trade that another broker has already set up or placed. It is the broker-dealer on the other side of a market transaction. In short, for a broker willing to sell (or buy), the contra broker would be willing to buy (or sell).

For instance, a contra broker may be a party that assumes the buyer’s side in a transaction in which another party is poised to sell securities in the market.