The 31-year-old former top-10 player retired in 2008 because of a shoulder injury but played sparingly over the next three seasons.
His last professional match was in 2011, but he asked for a wild card into qualifying in Stockholm and promptly won three matches.
Johansson has insisted this is a one-off, but he was hugely impressive in a 6-1 6-3 victory over Alejandro Falla.
Next up for Swede is a clash with second seed Milos Raonic, who needs a good week to boost his hopes of qualifying for the Barclays ATP World Tour Finals in London.
American Jack Sock will meet top seed David Ferrer in round two after seeing off fellow young gun Bernard Tomic 6-4 6-2.
Fifth seed Ernests Gulbis was pushed all the way by Jeremy Chardy before sealing a 6-3 3-6 7-6 (7/3) win, while seventh seed Grigor Dimitrov saw off qualifier Marius Copil 6-3 6-4.
There were also first-round wins for Spain's Guillermo Garcia-Lopez and Jan-Lennard Struff of Germany.