The Lake County School Board will investigate Jerry Buell, who was suspended from the classroom on Wednesday and reassigned to administrative duties.
Buell told the Orlando Sentinel that he wrote the post on his own time on his personal computer.
Buell is a veteran social studies teacher and one-time school Teacher of the Year. He wrote in a July 25 Facebook post that he "almost threw up" after watching a TV news story about legalized same-sex marriage in New York.
The district now must determine whether Buell violated the school's code of conduct.