Curtis Martin made a layup with 1:21 left in overtime to pull Mount Saint Mary's into a 67-all tie, but a layup by Cannon with 49 seconds left gave the Terriers the lead for good.
The Mountaineers went 0 for 4 from the field from there and two free throws apiece by Cannon and Brent Jones completed the scoring.
Jones finished with 18 points, nine rebounds and five assists for St. Francis (13-9, 7-2 NEC).
Junior Robinson scored a career-high 22 points for Mount St. Mary's (9-11, 5-4), which shot 49 percent from the field, but was outrebounded 40-24, including 16-4 on the offensive glass.
St. Francis held an 18-2 advantage in second-chance points.
Cannon became just the fourth player in Northeast Conference with at least 1,000 career rebounds (1,004).