The club announced that it fired the veteran manager on Tuesday afternoon, after just one season under Guillen.
The Marlins had high expectations heading into the season after spending a ton of money in the offseason. Instead of living up to those expectations, they fell flat on their faces, finishing 69-93, which put them in last place in the NL East.
"After careful consideration following the disappointment of the 2012 season, we decided to dismiss Ozzie," Marlins president Larry Beinfest said.
The outspoken Guillen didn't help himself much dating back to the beginning of the season. His controversial comments about Cuban dictator Fidel Castro caused an uproar in Miami, a city with a large Cuban population.
Guillen also caused a stir in a dispute with closer Heath Bell, a tussle that eventually went public. The reliever was shipped to Arizona last week.