Defending champion Murray prevailed 7-6 6-4 after weathering a storm from his 21-year-old Bulgarian opponent in the opening set.
The US Open champion played a flawless tiebreaker to win it 7-0 and a clinical second set allowed him to recover a service break and complete ideal preparations for the Australian Open, which begins at Melbourne Park on Jan. 14.
"I'd like to dedicate this victory to one of my best friends back home," Murray said in his speech at the presentation. "You're going to be okay. You're going to get through."
When Murray signed a television lens after the match, he wrote "For You .....", the third word being indecipherable.
He was asked about the dedication in his post-match conference and replied: "Just a sick friend."
Murray's secrecy mirrored his comments after his matches at Wimbledon and the US Open last year when he pointed both index fingers to the sky after all of his matches.
He made the same gesture after beating Dimitrov in his final tournament before the Australian Open, but was earlier in an agitated mood when the Bulgarian raced to a 5-2 first-set lead.
The 25-year-old Scot said his typically negative body language was due to unrealistic expectations of perfection.
"I think it depends how much it affects you in terms of duration of time," he said of his self-admonishment.
"I mean, if it's one point, and you get annoyed for 15 seconds afterwards, and you can get back to playing the next point with good intensity, then it's fine.
"When I was younger, it used to last quite a long time and it would take me a while to get back into it.
"Today, I started the match off badly and came back into it. I had lost serve in the second set and broke back straight away and won three games in a row to win the match.
"So long as it's not affecting me for long periods or when I go behind and I'm not finding ways back into matches, that's when you get worried.
"Sometimes you're maybe looking to play perfect tennis all the time. That's never going to happen. It's something you need to accept."
Dimitrov pushed Murray to the limit with an array of blazing groundstrokes and looms as a dangerous presence in the Australian Open draw.
He denied fearing any of the top three players in the world: Novak Djokovic, Roger Federer or Murray.
"Fear?" he said. "Why fear? Why do I have to feel intimidated? I want to play them. I want to play them all.
"There's nothing better than to play against these guys and do the best you can against them. Eventually, long-term, if you want to be good you're going to play them almost every week." — Reuters