The 23-year-old, who joined the Pilgrims in January from Kettering Town, was an outstanding performer as United climbed away from danger at the foot of National League North.
The Sutton Coldfield-born stopper kept six clean sheets in 17 appearances for the Pilgrims.
Gregory has now put pen-to-paper on a new deal at the Jakemans Community Stadium – as Ian Culverhouse's recruitment drive clicks into gear ahead of the move to a hybrid training model for the new season.