As no candidate secured a majority of the vote (50% of all votes cast +1), a runoff was held on June 8, 2019, between the two top candidates, incumbent mayor Ron Nirenberg and San Antonio City Councilman Greg Brockhouse.

[3] In the 2017 San Antonio mayoral election, Nirenberg became the first person in twenty years to defeat an incumbent mayor when he defeated Ivy Taylor in a highly contested runoff election.

During his tenure in office, Nirenberg's progressive platform was often criticized and challenged by Greg Brockhouse, a more conservative member of the San Antonio City Council who also took office in 2017.

[4][5][6] Brockhouse repeatedly stated that he would challenge for the mayor's office when the 2019 elections were held.

None of the leading candidates received more than 50% of the vote and as a result, a runoff election was scheduled for Saturday, June 8, 2019, between the top two vote-getters.