The third-seeded Rebels (25-8) came here needing wins to sharpen their postseason resume. Now they will play No. 13 Florida, a 61-51 winner over Alabama, in Sunday's championship game where the winner advances to the NCAA tournament.
Reginald Buckner also had 15 points, and Murphy Holloway added 12 for Ole Miss. The Rebels now have won six of seven to reach the championship game for the first time since 2001. Another win would give coach Andy Kennedy his first NCAA berth and the Rebels' first since 2002.
No. 10 seeded Vanderbilt (16-17), the defending tournament champion, lost for only the second time in eight games. Kedren Johnson had a team-high 12 points.
Kennedy, the Rebels' winningest coach, has at least 20 victories in four straight seasons and became the fifth SEC coach to win 20 in six of his first seven seasons, but missing out yet again on an NCAA berth could threaten his job security.
The Rebels played without point guard Jarvis Summers, who hit his head hard in Friday night's win against Missouri. They didn't need him as they wore down Vanderbilt, with the Commodores playing their third game in as many days along with going to class the past two days.
Ole Miss outshot Vandy 44 percent (22 of 50) to 33.9 percent (19 of 56) as the Commodores went a chilly 6 of 30 behind the arc. The Rebels also finished with a 41-36 edge on the boards.
Ole Miss didn't grab its first lead until the opening minute of the second half, but the Rebels took control with a 15-2 run a few minutes later.
Vanderbilt was up 34-30 off a fast-break layup by Dai-Jon Parker with 15:13 remaining. Then Henderson got the Rebels going with a 3. He added another jumper for the fourth and final tie at 36. Buckner then scored on a three-point play. By the time Buckner hit two free throws with 9:10 left, Ole Miss had its biggest lead yet at 45-36.
Ole Miss led by as much as 58-40 on a dunk by Buckner with 3:20 to go. Vandy, which averaged 10 made 3-pointers in winning its first two tournament games, missed its first 10 to start the second half. Johnson hit the 11th with 2:07 left to cap a quick seven points for the Commodores, except it was too late.
This was a big change from Jan. 15 in the only previous game between these teams this season.
Vandy hit a Memorial Gym record 17 3-pointers in a game Ole Miss pulled out 89-79 after Henderson beat the buzzer with a 35-footer to force overtime. The Commodores blew the win by not even defending Henderson in the final seconds of regulation in that game, their third loss to open league play.
Vandy led 23-14 with 7:09 left on a free throw by Johnson.
Henderson, the SEC's leading scorer, missed his first five shots before finally scoring on a layup with 4:29 to go. He also added a jumper and then his first 3-pointer as the Rebels finished the half on a 12-3 run to tie it up for the first time at 26.