The Panthers (21-17) and Cougars (19-17) play Friday in Pittsburgh for the title.
Reggie Moore, who scored 16 of his game-high 18 points for the Cougars in the second half, tied the game at 49 with two free throws with 1:41 left in the game.
Lamar Patterson answered right away with a jumper and Pitt reclaimed the lead. Patterson scored 12 for Pitt.
DaVonte’ Lacy and Abe Lodwick each scored nine for WSU.
The Panthers played the game without senior guard Ashton Gibbs, who missed his first game of the season with an injured right ankle.
Gibbs, an all-Big East honorable mention and the conference preseason player of the year, had sat out practices on and off this season because of the ankle but had not missed a game.
He has averaged 14.6 points and 2.1 assists this season and scored seven points on 2-of-7 shooting Monday in a 67-66 loss at Washington State.
Washington State scored only 20 first-half points, the fewest Pitt had allowed in any half this season, and trailed by nine at the break. But the Panthers went 7:06 in the second half without making a basket, to keep the game close.
After shooting 51.2 percent from the floor and 60 percent from 3-point range on Monday, the Cougars shot 43.6 percent from the floor, and 4 of 13 from 3-point range.
The Panthers used an early 13-2 run that included 3-pointers from Tray Woodall, J.J. Moore and John Johnson to grab the lead.
Forward Nasir Robinson, who had made his first 3-pointer of the season Monday, hit his second with 43 seconds left in the first half. That gave Pitt its largest lead of the game, 29-18.
Washington State Notes:
Moore scored 16 of his 18 points in the second half.
Reggie Moore finished with just two assists, but has 188 on the season, just four away from the school single-season record of 192 set by Donminic Ellison in 1995.
The third and final game of the CBI Championship series will take place Friday, March 30 at 4 p.m. PT, 7 p.m. ET, at Petersen Events Center in Pittsburgh.
Fridays matchup will mark the third time WSU has played an opponent at least three times this season, as the Cougars went 3-1 against Oregon State (two in the regular season, one in the Pac-12 Tournament and once in the CBI).
Brock Motum did not play after spraining his ankle March 21 at Oregon State.