The two Americans split the first 10 games before Williams pulled away to win 7-5, 6-3. The victory was her 102nd at the tournament, breaking the tie she held with Chris Evert for the most by a woman in the Open era.
Williams hit 13 aces and lost only six points on her first serve.
Williams, who turns 39 this month, has won the tournament six times and has been runner-up each of the past two years. She’s seeded No. 3 and hoping to tie Margaret Court’s record of 24 Grand Slam singles titles.
Earlier, Garbine Muguruza opened the second day of the tournament by dedicating her win to a former top-10 player who had just revealed her cancer diagnosis.
Suárez Navarro revealed in a tweeted video that she’ll need six months of chemotherapy to treat Hodgkin lymphoma.
“I was expecting to see her in this tournament,” Muguruza said. “You know, she’s such a nice woman, so sweet, so kind, so humble.
“I, for sure, will dedicate this win to her because I want her to feel that we are behind her, that I am behind her, and I will go and see her at some point when it’s fine.”
Navarro, who turns 32 on Thursday, was ranked as high as No. 6 and has reached Grand Slam quarterfinals seven times, including at Flushing Meadows in 2013 and 2018.
Information from The Associated Press was used in this report.