Sotloff, aged 31, was beheaded by Islamic State militants in a video released on Tuesday, two weeks after the similar video of US journalist James Foley was posted online.
"In honour and in memory of Steven Sotloff, I hereby direct the flags of the United States and the state of Florida to be flown at half-staff at all local and state buildings, installations, and grounds throughout the state of Florida", Governor Rick Scott said in a statement.
Sotloff was kidnapped 4 April 2013 in Aleppo near the Turkish border, but his abduction was kept secret after his family requested a media blackout.
His family on Wednesday paid tribute to the slain journalist, remembering him as a thoughtful man who enjoyed simple pleasures and was fascinated by the Middle East.
Sotloff was a freelance reporter who had written for Time magazine, Foreign Policy and other outlets. He was born in Miami.