The membership of the Finnish Seamen’s Union elects from amongst its members delegates for the Union Congress, which convenes every fourth year. The Union Congress is the highest decision-making body of the union. The delegates are elected by the members voting in an election and each local trade union branch forms its own electoral district. For each electoral district, one (1) delegate will be elected per each block of 200 members or part thereof who have the right to vote or are entitled to be elected. In the 2004 Union Congress there were 50 elected delegates.

The Union Congress determines the general policy of the union for the next four years. During the Congress, decisions are also made about the rules of the union and about initiatives put forward by local trade union branches or individual members.

The Congress chooses the members of the Executive Committee and the General Council.