Austin will play in a new $225million stadium and will be Texas' third MLS side, joining FC Dallas and Houston Dynamo.
However, Austin will become the city's first team in a major professional sports league.
"Austin is a thriving metropolitan city – the personification of what we mean when we say MLS is a 'League for a new America,'" Garber said in a statement. "We are extremely proud to be the first major professional sports league to become part of the culture of this historic American city."
Austin mayor Steve Adler said the city would be positively impacted by the addition of the club.
"This is a historic day for Austin, as MLS becomes the first major league to plant roots in our beautiful city," Adler said. "We believe professional soccer will bring a great and especially needed benefit to our city."
Other expansion teams that have yet to make an MLS debut will be located in Cincinnati (2019), Miami (2020) and Nashville (2020).