Johnson can play three more college seasons after the decision announced Thursday.
The 6-foot-3, 215-pound quarterback was granted the additional year after seeing action in just one of his first three seasons. He was redshirted in 2016 and missed all of last season with a foot injury.
Johnson appeared in nine games as a reserve quarterback and holder in 2017. He appears likely to be the starter when Georgia Tech opens the season Aug. 29 at defending national champion Clemson.
The NCAA's decision was similar to the one in late July that gave linebacker David Curry a sixth year. He has two seasons of eligibility remaining.