The 32-year-old Johansson staged a mighty fighback, saving four Blake match points in a dramatic 12th game of the final set.
The victory halted Blake’s winning run in the Swedish capital at 13 straight matches, which led the world number seven to titles in 2005 and 2006.
It also backed up the Swede’s Davis Cup victory last month over the American in a losing semi-final effort at Gothenburg.
Both men struck 10 aces with Johansson playing tough defence as he saved a dozen of 14 break points.
The unseeded Swede, ranked 55, will play for pride on Sunday when he faces the huge serve of Ivo Karlovic.
The impressive Croatian fired off four straight aces to easily dig himself out of danger and wrap up a 6-4, 6-3 semi-final win over German Tommy Haas.
Johansson improved to 24-11 at the Kungligahallen where he has won two of his nine career titles (2000 and 2004). He and Karlovic stand 2-2.
Blake took treatment on his back stretched out on court while trailing 0-5 in the second set.
“It was really sore at start of week from the flight over,” he said. “It never fully healed. I’m hoping it’s something simple or something out of place that can be fixed.”
Karlovic, who has shot into the Top 25 after standing outside the 100 mark at the start the season, was untouchable on serve with 15 aces in the 74-minute contest.
The seventh seed remains in dominating position against Germany’s Haas, with wins in four of their five meetings including another this season on clay in Houston.
Haas’ defeat presents an opportunity for Blake who goes into his semi-final standing tenth in the race for one of the eight spots in next month’s season-ending Masters Cup in Shanghai.
Should the American lift a third consecutive title at the Kungligahallen, he will rise to provisional seventh with three more weeks of ATP regular season competition remaining from Monday.
Haas began this week at 12th and had moved up to eighth by reaching the semis, according to ATP calculations.
Karlovic lifted the first set as Haas double-faulted to give it away, then broke the German fourth seed on his sixth opportunity of the sixth game of the second set for 4-2 command.
That success set the stage for Karlovic to again use his huge serve to best effect.
He saved three break points in the final game and fired his third untouchable serve in succession to set up a match point – also converted with an ace.
The Croatian was playing his third semi-final in seven weeks after New Haven and Tokyo.