Mica was a member of the Florida House of Representatives from 1976–80 and served on several committees, including the Appropriations Committee. He was a staff member for Senator Paula F. Hawkins from 1981–85 and became her chief of staff.
;1992 In 1992, Mica ran for Congress in the 7th District, previously the 4th District represented by two-term Republican Craig T. James. Mica won the Republican primary with 53% of the vote, defeating State Representative Richard Graham and Vaughn Forrest. In the general election, he defeated Democrat Dan Webster 56%–44%. ;1994–2004 During this time period, he won re-election every two years with at least 60% of the vote. Darrell Issa on the Navigation bridge of the USS Carl Vinson in 2014. ;2006 Mica defeated Jack Chagnon 63%–37%. ;2008 Mica defeated Faye Armitage 62%–38%. ;2010 Mica defeated Heather Beaven 69%–31%. ;2012 For his first 10 terms, Mica represented a district that stretched from the Orlando suburbs through Daytona Beach all the way to St. Augustine. After the 2010 Census, the bulk of Mica's territory became the 6th District. However, most of the Orange County portion, including Mica's home in Winter Park, was drawn into the new 7th District. That district had previously been the 24th District, represented by freshman Republican Sandy Adams. Although the new 7th was over 58 percent new to Mica, he defeated Adams in the Republican primary with 61 percent of the vote. In the general election, Mica defeated Jason Kendall 59%–41%. ;2014 Mica defeated Wes Neuman 64%–32%. ;2016 A court-ordered redistricting made the 7th slightly friendlier to Democrats. The new map cut out the district's share of Volusia County, while pushing it farther into Orlando. The 7th had already been a marginal district, even though Mica had been elected twice from this district without serious difficulty. Mitt Romney narrowly won it over Barack Obama in 2012, with 51 percent of the vote. In contrast, had the redrawn 7th existed in 2012, Obama would have won it with 49.4 percent. In the general election, Mica lost to Democrat Stephanie Murphy by a margin of 51%–49%.
Policy positions
Abortion
Mica opposes abortion. Regarding taxpayer funding of abortion through Planned Parenthood, he has said "I think the majority of Americans would oppose public, federal dollars going into abortion."
Mica supports Amtrakprivatization. In 2009, he earmarked $13 million for the Central Florida Commuter Rail, which was supported by a client of Mica's daughter. Mica has been opposed to the federal government contributing any additional funds towards repairing the Washington DC Metrorail system.
Marijuana
As chairman of the House Oversight Committee's subcommittee on government operations, Mica convened a hearing on marijuana legalization in 1999. It was the first such hearing since 1988. Mica opposes the legalization of recreational marijuana. Another such hearing was held by Mica in 2014 on the same subject, with multiple drug experts providing input.