[2][3] Betos played collegiate soccer at the University of Georgia and signed her first pro contract with the USL W-League Atlanta Silverbacks in 2009.

Prior to the founding of the NWSL, she played for Club Atlético River Plate, Apollon Limassol, and WPSL Elite teams Boston Aztec and New York Fury.

She signed with Seattle Reign FC ahead of the NWSL's first season, starting in seven league matches while Hope Solo recovered from a wrist injury.

Betos was selected by Racing Louisville in the 2020 NWSL Expansion Draft and went on to captain the team during their inaugural season, starting in 20 league games.

Born in Queens, New York to parents Luke and Susan Betos, Michelle began playing soccer at age five at the urging of her father, a one-time semi-professional player in Greece.

She played for the Albertson Fury '87 from 2004 to 2006, during which time she was coached by Paul Riley,[5] and was a member of the Region I Olympic Development Program (ODP) team in 2006.

In 2005, she was named an ENYSSA State Team player and participated in the Super Y-League Olympic Development Program (ODP) National Camp.

She was named W-League Goalkeeper of the Year after leading the Atlanta Silverbacks to the regular season Southeast Division title.

[5] Betos signed with the New York Fury in the Women's Premier Soccer League Elite for the 2012 season, where she was reunited with former youth coach Paul Riley.

[17] Betos was part of the 2016 Thorns team that won the NWSL Shield,[18] making 14 appearances with Adrianna Franch starting in the other six games.

[19] In September 2015, Betos joined Sydney FC on loan for the 2015–16 season, helping the team to a place in the 2016 W-League Grand Final.

Following the signings of Abby Smith and Mandy Haught, Betos did not feature in the 2023 season, which ended in a sixth-place finish and an NWSL Championship win.