Johnson completed a sensational performance in which he scored 34 of his 42 points in the second half -- scoring his team's last 21 points and rallying the Grizzlies from a 22-point deficit in the title game of the Big Sky Conference Tournament.
Montana will appear in the NCAA tourney for the second time in four seasons.
Johnson was 13-of-22 from the field and 14-of-14 from the foul line. He had never scored more than 32 in a game prior to Wednesday.
The Grizzlies will take a 22-9 record into the NCAA Tournament. Weber State fell to 20-10.