The Austin Fire Department and Lake Travis Fire and Rescue discovered the three-story building destroyed by fire around 3 a.m. in the 4700 block of Doss Road in Hudson Bend.
The mosque, which was under construction, burned to the ground. The cause of the fire is under investigation, authorities said.
No one was injured in the blaze, the Dallas News reported.
Jazak Allah-o-Khair with the Islamic Center of Lake Travis posted on Facebook to urge everyone not to make assumptions about the cause of the fire.
"This is a great loss to us," said Allah-o-Khair. "We are requesting the community to restrain from drawing any conclusion before the investigation is completed."