Argyle took the lead in the 40th minute at Home Park when on-loan Yeovil striker Reuben Reid swooped to score after Joe Bryan's thumping left-foot drive from 20 yards bounced off the post.
The dominant Pilgrims doubled their lead in the 54th minute following a brilliant run by left-back Onismor Bhasera whose pace-driven cross flew off Town's Michael Hector and in.
Argyle could have surged further ahead but Town number one Scott Brown saved well from Reid twice in two minutes.
Brown then did well to deny Andres Gurrieri as the Argentinian winger followed-up Reid's second effort.
At the other end, substitute Kaid Mohamed had his 12-yard shot on the hour saved by keeper Jake Cole's outstretched leg.
Brown had a busy afternoon and again did well to deny Gurrieri and then man-of-the-match Bryan.
Reid nearly claimed his second goal with 10 minutes left but his measured sidefoot shot spun off the post.