Tiafoe set the tone early, breaking serve in the opening set and remaining composed on his own delivery to keep Fritz from settling.
He carried that momentum into the second set, again striking early and dictating from the baseline to wrap up the win and snap a seven-match losing streak against Fritz since his first victory in 2016.
"I don’t even know what clip I was serving in the first set, but I felt like I couldn’t miss one," Tiafoe said.
"I returned really well. I had no troubles on my serve the whole match, and it just feels good to get this done.
"He’s a hell of a player and a hell of a competitor, too. I knew he was going to make it hard out there at the end, and I played some great tennis. Luck was on my way a little bit."
The 28-year-old dropped just seven points on serve in the final to cap a memorable debut appearance at the German grass event, as well as claiming his fourth career title and first in three years.
He also registered three top-10 wins during the week, including victories over world number 10 Flavio Cobolli and number four Felix Auger-Aliassime.
Before Sunday, Tiafoe had gone 0-4 in finals above ATP 250 level, including a defeat to Fritz in Tokyo in 2022, and had suffered a five-hour, 26-minute fourth-round loss to Matteo Arnaldi at the French Open earlier this month.
"This is big. I just want to say one of my favourite scriptures: 'The pain that you’re feeling does not compare to the joy that is coming.' Obviously, that has been proven very true," Tiafoe said.
"It’s something I’ve been living by."
The Halle triumph will see Tiafoe climb nine places to 19th in the ATP rankings on Monday, boosting his prospects ahead of Wimbledon, which begins on June 29th.