The Polish superstar extended her winning streak to 17 matches - including an unbeaten run at the United Cup - with the 7-6 (7-2) 6-2 triumph.
"It wasn't easy at the beginning to find my rhythm," said Swiatek.
"I felt a little bit off and I feel like Sofia really did everything to keep it that way."
Kenin served for the opening set in the 10th game but was unable to press home the advantage, leaving the door open for the free-swinging Polish four-time grand slam champion.
Swiatek, 22, was unable to convert her first set point in the 12th game but stepped up in the tiebreak as Kenin struggled to keep her emotions in check on a hot day in Melbourne.
The second set was a more straightforward affair, with Swiatek reeling off the last four games in succession to claim the victory in one hour and 51 minutes.
"Tennis is a pretty tricky sport where with the draws you can play former champions, former world No.1s and really experienced players (early on)," said Swiatek.
"You never know, so you just have to be ready, no matter what."
Kenin's run to victory at the 2020 Australian Open included a heart-breaking triumph over then-world No.1 and title favourite Barty in the semi-finals.Â
It doesn't get any easier for Swiatek, who will face Danielle Collins - runner-up to Ash Barty two years ago - in round two after the American beat three-time major winner Angelique Kerber 6-2 3-6 6-1.
Competing in her first major since 2022 Wimbledon after giving birth and spending 17 months off the tour, Kerber pushed Collins all the way.
But the 35-year-old German ultimately suffered the same first-round exit as fellow new mum and two-time Open champion Naomi Osaka, with Collins proving too powerful as she racked up 43 winners to 13.
Angelique Kerber's Melbourne Park comeback has been short-lived, the 2016 champ out in round one. (Lukas Coch/AAP PHOTOS)
In other action on Tuesday, Russian 14th seed Daria Kasatkina was made to work hard by American Peyton Stearns before advancing 6-2 3-6 6-2.
Other first-round winners were Italians Elisabetta Cocciaretto and Martina Trevisan and Denmark's Clara Tauson.
Later on day three, former world No.1 and dual Open champ Victoria Azarenka faces a potentially awkward first-round-encounter with Italy's Camila Giorgi.
Another major champion, 2017 French Open winner Jelena Ostapenko from Latvia, plays Australian wildcard Kimberly Birrell.
In the night session, women's third seed Elena Rybakina from Kazakhstan squares off against Czech Karolina Pliskova, while No.5 Jessica Pegula from the US starts her Melbourne Park campaign against Canadian Rebecca Marino.
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