The fire was reported about 2 a.m. Friday at the Islamic Society of New Tampa, fire department public information officer Corey Dierdorff said.
Firefighters arrived and quickly put out the fire at an entrance to the building, CNN affiliate WFTS reported.
Nobody was injured in the blaze.
Authorities have not decided if the fire was a hate crime, but Tampa Mayor Bob Buckhorn said at a news conference: "This is no different than the wave of anti-Semitic attacks on Jewish community centers
and synagogue and bomb threats that have been called in all across the country, including in Tampa over the recent months."
He said the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) will investigate along with the local fire department.
Thania Diaz Clevenger, civil rights director for the Florida chapter of the Council on American-Islamic Relations (CAIR), said community members worry they're being targeted because of their faith.
"Their fear is that it's hate-related, but it's too early to say if it is or isn't," she said at a news conference outside the mosque.
Rasha Mubarak, regional supervisor for CAIR-Florida, urged local, state and national officials to take a stand. Otherwise, she said, "It can give the green light to harm others."
Fire investigators will review surveillance-camera footage to try and learn more about who started the blaze, CNN affiliate WFTS said.
Diaz Clevenger said mosque members appreciate the outpouring of support from the community. She said a "solidarity gathering" will be held at 7 p.m. Friday outside the mosque.
Most of the recent publicized threats against faith-related groups have targeted Jewish community centers.
Forty-eight Jewish community centers in 26 US states and one Canadian province received nearly 60 bomb threats during January, according to the JCCA, an association of JCCs
On February 20, another wave of bomb threats hit 11 JCCs across the country, bringing the total to 69 incidents against 54 JCCs in 27 states, according to the JCCA.
Vandals also damaged more than 100 tombstones
earlier this week at a Jewish cemetery outside St. Louis.