Raiders have now lost their last 24 matches against the Riders – a run stretching back to 2012.
Leicester’s defence came through for them after they had been nine points down, as they held their visitors scoreless for seven minutes over the third quarter break.
In that time, Riders scored the last 11 points of the third quarter and the opening seven of the fourth, with big man Wayne Martin getting seven of those, for a 74-64 lead.
Plymouth were level late on, only for JR Holder to score consecutively inside the final minute.
Raiders’ Josh Wilcher was the game’s top scorer with 25. Leicester’s JR Holder scored 21 with former Raiders Pierre Hampton netting 19, which was also the number of points Donte Nicholas scored.