The 12th Mississippi Legislature met in Jackson from January 5, 1829 to February 6, 1829.
As the incumbent lieutenant governor, A. M. Scott served as the ex officio President of the Senate. Non-senators David Gordon and Joseph Pearce were elected Clerk and Door-Keeper respectively.
William L. Sharkey was elected Speaker, defeating David Cleveland in a 19-16 vote. James Cornell was elected Clerk of the House. Dillard Collins was elected Door-Keeper.