Greencastle Republican Haywood Ware will face Democrat William Dory in the Greencastle general election on November 3.
Ware defeated Jim Wright, who was arrested for driving under the influence after he crashed his car while driving on U.S. 231 in March.
Ware won with about three-fourths of the vote.
Dory ran unopposed on the Democratic ballot.
Current mayor Sue Murray is not seeking a third term.