Portsmouth dominated the first half and were rewarded just before the interval.
Conor Chaplin’s right-wing corner was clumsily scuffed away by Richard Kone as far as Devlin, who fired home from near the penalty spot.
The goal came as no surprise as the hosts had been well on top, with Chaplin’s deliveries and winger Harvey Blair, who played in the absence of the injured Josh Murphy, causing QPR problems.
Colby Bishop headed against the near post from Chaplin’s early corner, headed a Chaplin cross wide, and brought a save from keeper Ben Hamer with a left-footed strike before Pompey eventually took the lead.
But Rangers were better after the break and also scored via a right-wing corner, delivered by Nicolas Madsen, with Dunne getting in front of Bishop to plant a header beyond Nicolas Schmid.
Keeper Schmid then kept out a header from Kone, who also sent an effort well wide of the target as the R’s threatened to score again.
Portsmouth have struggled at set-pieces this season and conceding from one again proved costly.
They will hope for better at home to Charlton on Monday, while QPR will be away to West Bromwich Albion.
