The 20-year-old Tsitsipas became the youngest Grand Slam semifinalist since 2007 when the big-serving Greek reached the last four of the Australian Open earlier this year, getting the better of 20-time Grand Slam champion Roger Federer along the way.
"I found rhythm in the worst possible moment", Tsitsipas told the ATP Tour's official website.
Yet the Tsitsipas took his second break point, and the first set, when Kukushkin fired a backhand into the net.
Top-seeded Greek tennis sensation Stefanos Tsitsipas won his second second career ATP 250 title in Marseille at the Open 13 tournament.
"[I have] satisfaction. There was a lot of stress this week because I knew I had to face some good opponents..."
The Kazakh was first to secure his place in the final and Tsitsipas joined him by edging out Goffin in a tight first set before running away with the second to complete a 7-6 (1), 6-2 triumph.
"Winning titles is the thing that I am working for". I'm happy that I got through that stress and played the game that I was supposed to play.
Break points were in short supply in the opening set with neither player wilting under the pressure as they held serve.
Tsitsipas was seeing the ball very well on Kukushkin's serve and returns, hitting some juicy forehand and backhand winners straight down the line. The World No. 12 improves to 2-0 in his FedEx ATP Head2Head rivalry with Kukushkin, adding to his three-set win over the Kazakh at the Dubai Duty Free Tennis Championships past year.
After failing to convert his first break-point opportunity, Kukushkin claimed the opening break of the second set at 2-2 with his second cross-court forehand victor of the game.