A Republican, she has represented the 28th district, which includes Collier, Hendry, and part of Lee County in Southwest Florida, since 2016.

In 2010, when incumbent Republican state representative Tom Grady declined to seek another term in the legislature, Passidomo ran to succeed him in the 76th District, which stretched from Naples Park to Chokoloskee on the western coast of Collier County.

Advancing to the general election, Passidomo faced Libertarian candidate Peter Richter, whom she defeated in a landslide, winning her second term in the legislature with 79% of the vote.

In 2016, Passidomo ran for the Florida Senate District 28 seat vacated by Garrett Richter, who was term limited.

She defeated state representative Matt Hudson in the Republican primary, 58% to 42%, and faced only write-in candidates in the general election.