An ambidextrous thumb safety assembly, configured for use in a firearm, includes a first lever assembly for positioning on a first side of the firearm, a second lever assembly for positioning on a second side of the firearm, and a monolithic shaft assembly for coupling the first lever assembly and the second lever assembly. The monolithic shaft assembly includes a first support portion configured to rotatably engage a first portion of a frame of the firearm, a second support portion configured to rotatably engage a second portion of the frame of the firearm, and a control portion configured to selectively prohibit operation of a trigger mechanism of the firearm.