A wildcard for the Auckland event, Williams scored a 7-6 6-2 first-round victory over countrywoman Katie Volynets in their first round match on Monday night.
The 42-year-old, twice the age of her opponent, mustered all that experience and also showed plenty of class in what was her first competitive appearance since the US Open last August.
Williams' win followed a more straightforward first-round triumph for young Canadian third seed Leylah Fernandez.
The 2021 US Open finalist eased to a 6-1 6-1 victory over Czech teenager Brenda Fruhvirtova.
Earlier on the opening day, China's Lin Zhu bagged the first upset of the tournament.
The world No 84 fought back from a set down to eliminate sixth-seeded American Madison Brengle 4-6 7-6 6-4 in almost three hours.
Others booking their spot in the second round were Canadian eighth seed Rebecca Marino, Belgian qualifier Ysaline Bonaventure and Austria's Julia Grabher.
Top seeds in the doubles, New Zealand's Erin Routliffe and American playing partner Caroline Dolehide suffered an upset 7-5 6-4 defeat to Mexico's Fernanda Contreras Gomez and American Catherine Harrison.
Day two featured an impressive lineup, including top seed Coco Gauff and three former Grand Slam champions.
British star Emma Raducanu, who beat Fernandez in the 2021 US Open final, was first up on centre court against Fruhvirtova's older sister Linda.
Raducanu would be followed by Gauff, second seed and 2017 US Open winner Sloane Stephens and then another American, 2020 Australian Open champ Sofia Kenin.
