The 36-year-old new mother beat 29th-seeded Kiki Bertens of the Netherlands 7-6 (5), 7-5 on Saturday in the BNP Paribas Open, setting up a third-round showdown with her older sister, eighth-seeded Venus Williams.
She'll be taking on sister Venus in the third round and talked about playing the opponent that she does not like playing: "She's had such a good year last year and playing fantastic tennis".
Williams scuffled at times in the first set, but she showed a ton of grit and fight in battling from behind and overcoming adversity.
"I'm getting there. I have a long way to go". I'm still making errors that I don't normally make. "This whole month I am playing tournaments in California and Florida- both my home states", she wrote.
"Everything is a bonus", Serena explained after the second-round fixture, but added she "would prefer to play someone else, anybody else, literally anybody else" rather than her sister. It's never easy to play first match in any tournament, and in this tournament especially for me. I have such a long way to go. "It's just afterwards I don't like it as much".
Fans accused the siblings and their father Richard of being duplicitous, leading to Serena being booed during her finals encounter against Kim Clijsters.
The crowd's treatment led to a 14-year boycott by the sisters, which Serena finally ended in 2015.
Venus Williams readies to serve.
The two met last time in the 2017 Australian Open final, which Serena won.
This will be their 29th competitive meeting.
Serena Williams owns a 17-11 record against Venus Williams, having taken the most recent matchup in the final at Melbourne previous year.
Other second-round winners were No. 5 seed Karolina Pliskova, 7-6 (4), 6-1 over Irina-Camelia Begu; No. 6 Jelena Ostapenko stopped Belinda Bencic 6-4, 3-6, 6-1; No. 17 CoCo Vandeweghe defeated beat Kaia Kanepi 6-0, 7-6 (6); and Kristina Mladenovic edged Samantha Stosur 7-5, 7-5. This is the earliest they will face each other since then.
But when Richard Williams and Venus Williams arrived at the stadium two days later to watch Serena Williams play the 2001 final against Kim Clijsters, they were met with a chorus of boos from the crowd of almost 16,000 as the father and his daughter walked down the stairs to their courtside seats.