A Republican, Díaz was a member of the Florida Senate from 2018 to 2022, representing the 36th district, which encompasses the Hialeah area in northwest Miami-Dade County.

From 1995 to 1999, he taught social studies at Hialeah-Miami Lakes High School, where he spent eight years as an assistant principal.

[citation needed] Díaz denied allegations of discussions about drug use and inappropriate comments to a female student during his teaching career in the 1990s.

[4][5][6] In 2010, Díaz ran for the Miami-Dade County School Board, but lost to Perla Tabares Hantman in the primary, receiving only 39% of the vote to her 61%.

During the 2022 legislative session, Díaz was the sole Republican to vote against the congressional redistricting plan, thus signaling his allegiance to Governor Ron DeSantis.

Diaz said, "Sociology has been hijacked by left-wing activists and no longer serves its intended purpose as a general knowledge course for students.

"[13][14] While serving in the legislature, Díaz sponsored legislation that would "allow more private online education providers, some from outside Florida," to offer classes to public school students; allow students to take classes in public virtual schools in other counties, and require the Florida Department of Education "to create a catalogue of online offerings.

"[15] He rejected allegations of conflict of interest when, in 2017, he sponsored, along with Richard Corcoran and Michael Bileca, legislation that directed $140 million of public funds to charter schools.

"[20] Diaz was a four year letterman college baseball player at St. Thomas University where he played for head coach Al Avila.