Littler, who has averaged just shy of 101 for the season, entered the arena to raucous applause but was relatively slow out of the blocks, with Labanauskas holding the first leg with a tidy 130 finish on the bull.
The newly crowned number one swiftly responded, opting to avoid a 164 checkout and eventually taking out tops to level the score against the Lithuanian.
Labanauskas, ranked 95th in the world and a former World Championship quarter-finalist in 2020, was seemingly up for the fight, again holding to take the second leg.
Littler also held to force a decider against the throw, where The Nuke's scoring eventually came into play as he sealed the first leg with a 76 checkout, averaging over 103.
Labanauskas puts up fight
Despite a scare with darts in hand at the start of the second leg, Littler was able to hold, but Labanauskas again responded to level the set. Littler eventually took out 60 via double 10 to make it 2-1.
By this point, the 180s were flowing for both players as Labanauskas raised his average to just shy of 98, and eventually took out double 16 to send the second set to a decider, this time with Littler having the first go at the board.
A fifth 180 of the match - seventh in total - saw the world number one race to a finish, mopping up in 14 darts.
The third set began with a hold for Labanauskas, although Littler would reply with an excellent 124 finish on the bull - his first ton-plus checkout of the match and tournament.
A 120 finish would make it back-to-back ton-plusses to make it 2-1, and at a crucial moment in the match, to break throw.
The defending champion finally put the contest to bed with a 16-dart leg finished on double 6 to make his way safely into the next round with a 3-0 victory.
'10 days off'
Littler averaged 101.54 for the contest to Labanauskas' excellent 95.25, with 10 180s between them.
"It definitely wasn't easy. Looking at the stats, it didn't feel like that, but I'm happy," Littler told Sky Sports while fighting off wasps on the Ally Pally stage.
"There's a bit of nerves, but once you come here and you win a leg, two legs, then the first set, and that first set is crucial because it settles you down. As long as you win the sets, that's all that matters.
"Everyone in the tournament wants to win their first round. It's definitely the hardest game. If you don't play well, you won't win.
"The first game is done, and now I get 10 days off."
Littler will face either Mario Vandenbogaerde or David Davies in round two.
Bully Boy progresses
Earlier in the evening, Michael Smith, winner in 2023, beat Women's World Matchplay Champions Lisa Ashton in straight sets to progress in his 15th year at Ally Pally.
Ashton had initially taken the first leg but was unable to cope with the scoring power of Bully Boy, who stormed to the first set before almost hitting a nine-darter in the second.
Smith - ranked 28th - ultimately dominated the rest of the encounter, whitewashing the second set and dropping one leg in the third.
However, his doubles left a bit to be desired, missing seven match darts at the end prior to finally checking out on double 18.
"That first set, I was so nervous. I didn't want to lose that first set, and when I came back out, I was thinking they would be louder and louder, so I was trying to force things, and then I went 180, 180, and I thought 'I've got 60 grand here' but ended up missing," Smith told Sky Sports after his win.
"I had to keep focus. Not a great game. But I will take it, and I have 10 days off. Solid practice now and back on the 20th.
"I got the job done, will concentrate on the next one, and that's the main thing now."
Smith averaged 91.19 in the match, pinning three 180s to Ashton's one.
In a surprise result in the tournament opener, German debutant Arno Merk - ranked 163rd in the world - dismantled world number 53 Kim Huybrechts 3-1 in the first match of the evening.
Merk averaged 89.73, hit 40 per cent of his doubles and nailed three 180s, much to the delight of the relatively fresh-faced Ally Pally crowd.