Playing in front of a crowd of 2,638 at the Lund Center, the Vikings got 20 points and 14 rebounds, both game highs, from All-America forward Chris Braier.
Lawrence advances to play the No. 1-ranked team in the nation and defending national champion, the University of Wisconsin-Stevens Point, on Saturday at 7:00 p.m. at Quandt Fieldhouse.
Gustavus Adolphus finishes the season at 22-6 and saw its 18-game winning streak come to an end. It was the second consecutive season the Gusties lost a tournament game at home after being knocked out by UW-Stevens Point in the second round last season.
Kyle MacGillis added 14 points and Jason Holinbeck had 13 points on 5 of 6 shooting, including 3 of 4 from 3-point range.
Gustavus was led by Minnesota Intercollegiate Athletic Conference Player of the Year Doug Espenson, who finished with 15 points, but he got six of those points when the game was basically decided.
Lawrence (20-5), ranked 13th in the nation, used an outburst at the end of the first half to seize control of the contest.
The Vikings led 21-18 when MacGillis scored on a layup with 4:41 left in the opening half. After a miss by the Gusties, MacGillis hit a pair of free throws to put Lawrence up 23-18 qurg 3:52 left. Brett Sjoberg then drained a 3-pointer and Andrew Olson countered with a trey for the Gusties.
Holinbeck then hit a 3-pointer to put the Vikings up 29-21 with 1:58 left. After a miss by the Gusties, Dan Evans' layup gave Lawrence a 31-21 advantage. Sjoberg then drained another 3-pointer and the Vikings led 34-21 with 52 seconds left in the first half. Lawrence took a 34-22 lead into the locker room.
The Gusties didn't get closer than 13 points throughout the first 16 minutes of the second half, and the Vikings grabbed their biggest lead of the game, 19 points, at 58-39 with 3:35 left.
The Gusties countered with five consecutive points, but Brendan Falls nailed a 3-pointer with 2:05 remaining to take the steam out of Gustavus.
Trevor Wittwer countered with a 3-pointer for the Gusties, but Lawrence got a layup from Holinbeck to stretch the lead back to 63-47.
Gustavus' Adam TeBrake hit a long 3-pointer with 53.1 seconds left to cut Lawrence's lead to 64-54, but the Gusties would get no closer than 10 points.
MacGillis knocked down a pair of free throws with 46.7 seconds left, and Espenson followed with a dunk for Gustavus. The Vikings then made 4 of 6 free throws in the final 38.3 seconds to seal the victory.
The Lawrence win means a rematch of last season's Elite Eight tournament game against the Pointers. Stevens Point got late heroics from Nick Bennett to force overtime against the Vikings and then won it 82-81 to earn a trip to the Final Four.