Vernon came in for the injured Adam Rooney and was making his first start for Aberdeen since January. He wasted no time in opening his account, firing past Marc McCallum after just seven minutes.
United hit back through Sean Dillon before Vernon scored a second-half header. He rounded the keeper 15 minutes from time to complete his hat-trick after a mistake from Gavin Gunning, but speaking after the game Vernon insisted the three points were all-important.
"It's a funny old game isn't it, football," he said. "Obviously I'm delighted to get the three goals but ultimately the win for the team is massive tonight.
"We rode our luck at times through the game and the big man (goalkeeper Jamie Langfield) pulled off some incredible saves, so we're just delighted to get the result really."
He added: "When you're not getting as many games as you'd like, you're just determined to get in there and prove your point, like any other time I get a game I want to score goals, that's my job and thankfully tonight I've done that."
Aberdeen manager Derek McInnes paid tribute to the returning striker for an excellent all-round performance.
"He was absolutely fantastic," McInnes said. "He led the line well, he put himself about, was a goal threat and linked the play well. He was different class.
"He has had to be patient because we have been pleased with what Adam has given us.
McIness also hailed the display of veteran goalkeeper Langfield.
"Scott more than anybody does the extra work to keep his fitness up and make sure he is ready when called upon. He's a great pro," McInnes added.
Dundee United manager Jackie McNamara agreed with McInnes that Langfield had been the major difference between the two sides and feels his side were made to pay for individual errors on the night.
"I think they didn't deserve to lose," McNamara said. "We're disappointed with the goals we lost.
"I thought we had enough chances, and I thought Langfield kept them in it in the first half with so many saves he had.
"The chances were created but we didn't take them - the keeper was the difference on the night and concentration from the set-piece for the second one... and that last one was just comical defending.
"The lads that made mistakes have been punished today."