State elections were held in the Free State of Prussia on 20 May 1928 to elect all 450 members of the Landtag of Prussia.

[1] The governing coalition of the Social Democratic Party, Centre Party, and German Democratic Party retained its majority.

The SPD recorded its best result since 1919 while the opposition German National People's Party suffered significant losses.

The Centre Party, German People's Party, and DDP took modest losses; the Communist Party and Economic Party made modest gains.