In a release, Casada said he will not seek re-election in the August elections.
"This decision comes after much prayer and thought," Casada said in a release. "I am blessed and grateful to have served Williamson County and to have achieved many goals for my constituents, but it is time for a new chapter of public service."
During his tenure, Casada has served as a caucus chair, majority leader and speaker of the house, according to Casada's office.
In the last few years of his career, Casada has been the subject of some scrutiny. In 2019, he resigned as speaker of the house following an incident related to a former chief of staff and in January, current Speaker of the House Cameron Sexton, R-Crossville, announced Casada was the subject of a federal investigation.
Casada was first elected to office in 2001 and most recently served on the education administration and K-12 committees in the Tennessee General Assembly. He also served on the Williamson County Commission from 1994-2001.