Johnson alerted AllCyclones.com of the news Monday morning. He called head coach Paul Rhoads and Mark Mangino after practice.
"Long prayers and long conversation with my Mom helped me decide last night," Johnson said.
The Cyclones have been the favorite for Johnson since they offered in early June, but the recruitment's taken some time to play out. Two days before Iowa State offered, Johnson had committed to Tulsa. He preferred the Cyclones for a variety of reasons — the Big 12 factor, the Mark Mangino factor, the fact his cousin Jeremy Reeves had enjoyed his time in Ames — and those feelings were only enhanced when Johnson was able to visit Ames in late June for the Elite Junior Day. But still, Johnson didn't want to jilt Tulsa.
It wasn't until July 14 that Johnson withdrew his verbal pledge from Tulsa, officially making him a free agent. In a phone call the next week with AllCyclones.com, Johnson said it'd be tough for another school to best the Cyclones in the chase for his signature.
"It's gonna take a lot because I really liked my visit, really liked my coaching staff and really liked my players, the guys who'd come in with me and be in my class," he said.
In recent months Kansas State, TCU, Arkansas and Utah State have shown interest in Johnson, who caught 39 passes for 506 yards and five touchdowns as a junior. Tentative trips to Arkansas and K-State were planned at one time or another.
Growing up in Big 12 country, Johnson is well-aware of the history of Mangino, ISU's new offensive coordinator.
"They just picked up Mark Mangino from Kansas and he likes to win," Johnson told Scout on July 31. "Coach Rhoads is a great guy. I also like Tommy Mangino quite a bit, and he seems like a great coach and a great guy. It'd be nice to play for him."
Johnson is the first wide receiver (probably of two) in Iowa State's 2015 class. Late July saw ISU nab three-star offensive tackle Julian Good-Jones and three-star running back Devine Ozigbo. The quarterback's already in place with Austin-area signal-caller Dominic DeLira. Johnson communicates with each of those players in a 2015 class group text. Offensive guard Bryce Meeker was the first offensive commit of the 2015 class.
The 6-foot-3, 215-pound Johnson has worked to simultaneously add weight and gain speed this summer.