The University of Texas ordered the emergency evacuation after getting a phone call at about 8:35 a.m (1335 GMT) from a man with a Middle Eastern accent who claimed to have placed bombs across campus, spokesman Gary Susswein said.
"He said he was associated with al Qaeda and said the bombs would go off in about 90 minutes," he said.
The university, with about 51,000 students and 24,000 staff and faculty, posted an emergency alert on its website just before 10 a.m. (1500 GMT).
"Immediately evacuate ALL buildings and get as far away as possible. More information to come," it said.
Buildings at North Dakota State University in Fargo also were evacuated because of a bomb threat.
"NDSU is requiring all employees and students to leave campus by 10:15 a.m.," (1515 GMT), it said in a statement on its website.
It was not immediately clear if the two threats were related.