In the women's draw, in-form Jessica Pegula and teenage prodigy Coco Gauff were both emphatic winners on the first day of the opening Grand Slam of the year.
Men's top seed Nadal unleashed some of his trademark hammer forehands, but also 46 unforced errors, before wearing down Briton Jack Draper 7-5, 2-6, 6-4, 6-1 in blistering heat on Rod Laver Arena.
It put the 36-year-old Spaniard into the second round for a 17th time and stretched his win-loss record at Melbourne Park to 77-15.
He will next play Mackenzie Mcdonald, who beat fellow American Brandon Nakashima in a five-set thriller.
"Super happy to be back here in Australia one more time. It's like the 19th season in the professional tour so very excited about this new beginning," he said.
"It's a victory I needed. I played against one of the toughest opponents possible in the first round. He's young, he has the power and I think he has a great future in front of him."
But it was a tough slog for Nadal who had lost six of his past seven matches, including his opening two this year.
Little separated them in a first set notable for a bizarre incident in which Nadal complained one his of racquets had gone missing.
He kept his cool and waited for his chance, which came at 6-5 on Draper's serve when he earned a set point and converted with a searing cross-court winner.
But Nadal lost focus in the second set as Draper raised his game and raced to a 4-0 lead before sealing the set.
The Spaniard regrouped and broke early in the third set to move 4-1 in front, winning the long rallies. Draper needed repeated treatment on his upper right leg, but against the odds broke back before Nadal again stepped up.
Draper was clearly struggling, grimacing in pain at times, and Nadal showed no mercy to race through the fourth set to victory.
Nadal created history on the same court last year with his five-set victory over Daniil Medvedev in the final.
It saw him claim ownership of the record for most Grand Slam men's singles titles on 21 ahead of Novak Djokovic and Roger Federer.
He added a 22nd at Roland Garros, while Djokovic won Wimbledon to move onto 21.
Nadal's 2022 run in Melbourne came in the absence of nine-time champion Djokovic, who is back this year and begins his campaign on Tuesday.
In the women's draw, Pegula blitzed 161st-ranked Romanian Jaqueline Cristian on Margaret Court Arena 6-0, 6-1 in a 59-minute romp to signal her intent.
Fellow American Gauff was equally explosive in racing into the second round with a 6-1, 6-4 thumping of Czech Katerina Siniakova on the neighbouring Rod Laver Arena.
Gauff headed into Melbourne on a high after winning her third WTA title at the Auckland Classic, while Pegula was boosted by upsetting world No 1 Iga Swiatek at the United Cup.
The 18-year-old Gauff now faces a mouth-watering encounter against former US Open champion Emma Raducanu, who beat Tamara Korpatsch 6-3, 6-2, barely 10 days after the Briton exited the Auckland event in tears with an ankle injury.
It will be a first meeting ever between Gauff and the 20-year-old Raducanu, two rising stars of women's tennis.
"I'm really looking forward to this match," Raducanu said.
"I'm very up for it. Coco has obviously done a lot of great things and she's playing well.
"I think we're both good, young players, we're both coming through – part of the next generation of tennis really – it's going to be a great match."