The 22-time grand slam champion teamed up with Norwegian Casper Ruud to record a 6-1 6-4 win over second seeds Guido Andreozzi and Miguel Reyes-Varela on the Swedish clay.
It was Nadal's first appearance at the ATP 250 event since winning the singles as a 19-year-old in 2005.
Nadal elected to skip Wimbledon to prepare for the Olympics on the clay courts of Roland Garros, where he has won a record 14 French Open singles titles.
"Personally, I am happy and I think it was a good match. We played quite well in the first time we played together and I'm happy to be back here after almost 20 years," the 38-year-old said on court on Monday (Tuesday AEST).
"I have great memories from this place from 2003, 2004 and 2005, so I am enjoying this week and hopefully can keep going."
Nadal is also entered in the singles at Bastad and is drawn to play Leo Borg, the son of Swedish great Bjorn Borg, in the first round.
Nadal, who won an Olympic singles gold medal in 2008 and doubles gold in 2016, will team up with French Open and Wimbledon champion Carlos Alcaraz in the doubles in Paris.
His doubles match on Monday was halted twice due to rain delays, prompting a light-hearted jibe from Ruud, the world No.9 in singles.
"He is getting old, so I'm not sure how his body feels when he has to stop and start all the time, but he did well," said the Norwegian.Â
