The 23-year-old came from one set down to defeat his fellow American 3-6, 6-3, 7-5 for the fourth ATP Tour title of his fledgling career.
Shelton was nowhere in the opening set. Fritz needed just 26 minutes to wrap it up. But he found form in the second, saving two break points while converting his own late in the set to force a decider.
In the third set, Fritz was on the cusp of victory. He was 15-40 up and about to break serve, but Shelton rallied to save three championship points, break him in the next game and hold to oull off a thrilling victory.
"It feels amazing," Shelton told the press afterwards.
"I thank God, because I needed something supernatural to end up winning this tournament with all the holes that I was in. I feel grateful to play five matches out here with these crowds. The energy was amazing.
"I had to fight until the last minute. Fritz was playing very good tennis and I was struggling a lot with what he was throwing at me. I tried to be a competitor through and through, and I ended up coming out on top. I think it's a testament to the work me and my team put in."
The victory caps off a week of grinding for Shelton, as it was his fourth three-set thriller in a row in Dallas.
"Once I get a set, I feel pretty confident," he continued.
"Once I'm able to sink my teeth in and feel like I have some sort of rhythm, I just start to loosen up and find my level. I think I'm also in shape - my fitness levels are good - and that probably plays into it."