Seljaas chose the Cougars over Utah, Utah State and San Francisco.
"It was a tough decision and every school had a lot to offer, but BYU fit me best," he told the paper. "I live the style of play at BYU, the coaches are awesome and the school is a great place."
Seljaas averaged 15.0 points and 4.0 rebounds as a sophomore last season. He is the first commitment for BYU in the 2015 class.