Doidge's powerful strike on the half-volley just before the interval at Pittodrie means Aberdeen can no longer catch their Edinburgh rivals, who also have the Scottish Cup final to look forward to.
Welshman Doidge's strike was the highlight of a first half in which both sides played neat football but the goalkeepers were rarely tested.
The home side could have been in front after 39 minutes as Ryan Hedges' mis-kick presented Callum Hendry with an excellent opportunity 15 yards out, but the on-loan St Johnstone striker fluffed his lines and sent his effort well over the crossbar.
His profligacy was quickly punished, as Hibs were soon in front. Darren McGregor's long ball out of defence set up the chance, with Doidge working hard to win the ball before it sat up kindly for him to drill past goalkeeper Gary Woods from just outside the area.
Aberdeen could have levelled before the break as Hendry peeled off his man to meet Connor McLennan's right-wing cross with a powerful header, but Matt Macey was well-placed to grasp the ball.
Hibs should have been out of sight three minutes after the interval when Martin Boyle sized up a fine cross to the back post, but Jackson Irvine was unable to direct his shot on target after a good first touch.
The home side needed to win to stay in the race for third, and Hedges will have been disappointed with his finish into the side-netting after being granted all the time in the world to turn in the Hibs area.
Florian Kamberi also had a good opening after fine build-up play from Hendry in the area, but the Albania forward somehow sent his effort well wide.
The game opened up as Aberdeen pushed for a leveller, with Niall McGinn and Fraser Hornby thrown on in attacking positions, but Hibs were happy to soak up the pressure and hit on the counter, with their own substitute Jamie Murphy stinging the palms of Woods with a decent strike from distance.
And ultimately, Jack Ross' men did what they had to to seal that third spot they had targeted.