Penelas, an American of Cuban descent, attended college at St. Thomas University. In 1985, he received his law degree from the University of Miami School of Law, where he graduated cum laude and was inducted into the university's prestigious Iron Arrow Honor Society.
Penelas and his wife, Lilliam, have two sons, William and Christopher and a daughter Alexandra.
Penelas served on the city council of Hialeah, Florida from 1987 to 1990. In 1990, he became the youngest county commissioner in Dade County history. On October 1, 1996, Penelas became the first Executive Mayor of Dade County (which was renamed Miami-Dade County in 1997). Unlike the majority of Cuban American leaders in Florida, Penelas is a member of the Democratic Party.
In 1999, People Magazine named Penelas as "America's sexiest politician."
During the Elián González controversy in 2000, Penelas vowed that he would do nothing to assist the Clinton administration and federal authorities in their bid to return the six-year-old boy to Cuba.
Later, presumably in retaliation for the Clinton administration's handling of the Elian Gonzalez matter, Penelas refused to campaign alongside Al Gore during Gore's 2000 presidential bid, and made no comments during the controversy over Miami-Dade County's ballots in the aftermath of the election.
Critics allege that Penelas' failure to intervene in the Dade County ballot controversy, including failing to provide adequate security at the Dade County Building during the Brooks Brothers riot, was a contributing factor to George W. Bush's ultimate victory in the controversial election.
As a candidate in the United States Senate election in Florida, 2004, Penelas was unable to match the popularity or fundraising levels of rivals Betty Castor and Peter Deutsch in the August 2004 primary. His campaign was made more difficult when Al Gore termed him the single most treacherous and dishonest person I dealt with in the 2000 election. Gore's remarks hurt Penelas with Democratic voters. He lost the primary, winning a mere ten percent of the vote.
Penelas serves currently as a political analyst for Spanish-language Univision television.