She represented the South Australian House of Assembly seat of Taylor for the Labor Party from the 2010 election until her retirement in 2018.

[3] Vlahos was elected to the seat of Taylor after the retirement of the previous Labor member Trish White.

"[6] At the 2018 election, Vlahos would have been Labor's first-listed candidate on their upper house ticket,[7] but she quit before the publication of the ICAC report into the Oakden scandal.

Vlahos' elevation to the Cabinet of South Australia in the Jay Weatherill government occurred in January 2016.

[8][9] Vlahos represented the following portfolios in the Cabinet of South Australia:[10] She resigned from Cabinet on 17 September 2017 for personal health reasons, but announced that she intended to remain in the House of Assembly until the March 2018 election[11] After leaving parliament, Leesa became a board member for the following organisations: During 2022 she joined the Salzburg Global Seminar as part of the "Health and Economic Well-being: Gender Equity in Post-Pandemic Rebuilding" program[17]