The Flying Dutchmen trailed most of regulation, but gained a chance for the win when junior center Kyle Kleersnyder's putback at the buzzer left the teams tied 98-98.
Hope seized the momentum in overtime when junior forward Travis Spaman scored the team's first seven points.
The victory moved Hope to 15-3 on the season to mark the 24th consecutive year that coach Glenn Van Wieren's team has won 15 or more games.
Hope remains atop the MIAA standings with a 5-1 record, half-a-game ahead of Adrian and Albion who are each 5-2.
Hope had three players score 20 points or more. Sophomore forward Andy Phillips and junior guard Greg Immink each scored 22 points while Spaman tallied 20. Freshman Stephen Cramer added 16 points while Daane Griffeth and Kyle Kleersnyder followed with 15 and 12.
Hope ended with a 50-37 rebound advantage as Phillips pulled down 10 boards for his third double-double of the year.
Hope was able to overcome Tri-State's 16 three-point baskets by making 31-of-46 free throws, including 12-of-17 in the overtime.