The 6-foot-8 Flannigan chose the Vikings over DePaul, Wisconsin, St. Bonaventure, Xavier and Akron, among others.
"Every school who offered wanted me," he told the paper. "The biggest difference is Coach (Gary) Waters said he needs me. He wants me to come in and be a big part of what they are doing there."
Flannigan is the first recruit from the 2013 class for Cleveland State.