It was the West Country side's first league win since they beat Barnsley 3-2 on the opening day of the season.
QPR have faired even worse, loosing all but two matches this season, a record which leaves manager John Gregory under increasing pressure.
Despite the scoreline and Argyle's dominance of large periods of the game, QPR could have easily walked away with at least a point.
Daniel Nardiello struck the crossbar with a header early in the first half, while Ben Sahar's shot in the dying minutes looked destined for the bottom corner but Argyle keeper Luke McCormick stretched and tipped the effort around the post.
Hungarian international Peter Halmosi, fresh from international duty last week, scored Argyle's first in the 50th minute.
It was a goal worthy of an international occasion. Winger Halmosi jinked his way past a couple of stunned QPR defenders, having been well fed by striker Barry Hayles, and lashed home a stinging drive from the edge of the penalty area.
His first goal of the season had hit the back of the net before Lee Camp in the QPR goal could move.
It took little over ten minutes for Argyle to double their advantage as Rangers struggled to recover from Halmosi's strike.
Sylvan Ebanks-Blake nodded a long ball down to David Norris, who ran through on goal before firing hard past Camp from 12 yards out.