0920 GMT February 17, 2020
The 28-year-old will battle for the title against Moldova's Radu Albot, with both seeking to become the fifth first-time winner on the ATP Tour this year, AFP reported.
Albot, 29 and ranked 82nd in the world, defeated American Mackenzie McDonald 3-6, 6-0, 6-0 to reach his first tour-level final.
Evans reached his only other ATP final in 2017 when he lost at Sydney to Gilles Mueller of Luxembourg. He was suspended for one year later that year after testing positive for cocaine at the Barcelona Open that April.
Evans denied second-seeded Isner, 33, a chance at his 15th career ATP title, although he said that was the furthest thing from his mind during the match.
"I just play every match as it comes, every point, every game," Evans said.
"It sounds very cliché but I'm just playing every match.
"It's not about beating John, it's not about beating (Andreas) Seppi. The ball is coming and I'm just trying to focus on myself," added Evans.
In taking a 6-3, 2-2 lead, Isner stretched his streak of service games held to 77 – dating back to the first round of the Australian Open.
But Evans broke him three times from there to turn the tide.
"I returned really well when I got my racquet on the ball, and that was my goal," Evans said. "Just to get the ball back and get the running shoes on."