At the other end Newcastle bound Stephen Glass cut inside full back John McQuillan but then shot a foot too high.
Aberdeen then took the lead in 14 minutes. Joe Miller supplied the pass and Billy DODDS beat Saints defender Alan Kernaghan and fired home with a well executed low left foot shot.
Aberdeen broke upfield in 32 mins and Joe Miller tried a shot on the run, but driove it wide of the post.
St Johnstone almost grabbed the equaliser in 38 mins. George O' Boyle tried a close range shot, but the effort was deflected by Inglis and Leighton scrambled to dive on the loose ball.
The Dons finished the half strongly, winning two corners in quick succession but both proved fruitless.
Half Time - St Johnstone 0 Aberdeen 1
After the restart George O' Boyle weaved his way into the box but lifted his left foot effort too high. The striker then tried an effort from 18 yards, but was well off target.
St Johnstone were doing most of the attacking and fullback John McQuillan tried a powerful shot from 25 yards which keeper Leighton did well to stop.
Aberdeen managed to hold on to their slender lead which gave them only their second away league victory of the season.