Abstract: This invention is a transom-mounted combination casting seat and anti-drift fin, herein called a transom fin seat. The transom fin seat includes a fin stem, a fin deployed at the bottom of the fin stem, a rigid or pivoting casting seat affixed to the top of the fin stem and a mounting mechanism affixed to the fin stem for securing the transom fin seat to the transom of a boat. In a preferred embodiment, the mounting mechanism is characterized by a transom bracket attached to the fin stem and adapted for engaging the boat transom. In a most preferred embodiment, the transom bracket includes one or more screw-type clamps for removably clamping the transom bracket to the boat transom.