The Lancers held a lead as late 1:41 in the game, but couldn't seal the deal down the stretch, getting outscored 10-3 in the final minute.
The loss drops the Lancers to 6-2 overall on the season while Truman State improves to 7-1.
Despite shooting 37 percent from the floor and hitting just 1 of 4 3-pointers the Lancers entered halftime down just four, 32-28. CBU did hit all seven of its free throw attempts to help keep it close in the first half.
Truman State was also just 2 for 9 from beyond the arc, but managed a 44 percent shooting clip to take a lead into the half.
Uncharacteristically the Lancers were out-rebounded 20-13 in the opening period, giving up eight second chance points on seven offensive boards.
Jasmine Beverly and Megan Sharpe had nine points each in the first half to lead their respective teams.
A Beverly jumper narrowed the gap to two early in the second half and then a steal by Myriah Hicks followed by a dish to a cutting Lewis put CBU up 43-41 for the first time since 11:14 in the first half.
The two teams would trade the lead back and forth, heading into the final minute all knotted up at 63-63.
A 3-pointer followed by a steal on the defensive end from Amy Griggs helped lead to a five point lead for the Bulldogs after a pair of free throws.
Though the Lancers held a decisive edge all game at the charity stripe, it was Truman State down the stretch that made its foul shots to seal the win.
Hicks led all players with 14 points, while Lewis added 13 and Beverly had 12. No Lancer had more than four rebounds.
The Bulldogs had four players in double figures and were led by Becka McHenry and Megan Sharpe with 13.
Truman State won the battle on the boards 38-20.
CBU continues tournament play tomorrow, facing Southwest Baptist in the final game of the Ayres Inn & Suites Lancer Classic.