The 36-year-old tennis pro competed at the Fed Cup in Asheville, North Carolina, over the weekend, marking her first competitive match since giving birth to her first child, daughter Alexis Olympia, with husband Alexis Ohanian last September.
It was Serena's first competitive match since winning her 23rd major at the 2017 Australian Open.
Germany downed 2017 runners-up Belarus in Minsk 3-2 after Tatjana Maria and Anna-Lena Groenefeld won a tight deciding doubles against Aryna Sabalenka and Lidziya Marozava 6-7 (4), 7-5, 6-4. And although she and her sister, Venus, fell short during the doubles match, losing 6-2, 6-3 to Lesley Kerkhove and Demi Schuurs of the Netherlands, Serena appeared to be all smiles, thanks to her support system.
Early in the match Serena showed the effects of her lengthy layoff, perhaps most noticeably when she shanked a routine volley that left her bent over in embarrassment.
But no matter what happens next-whether she decides to retire and spend more time with her family, or she roars back to win another dozen or so titles-Williams has the satisfaction that she got to play in front of her most important fan.
'It's great. It's her first match so I'm glad she got to see it, ' Serena gushed at the Cellular Arena. "I feel like I'm on the right track for me".
But she was determined to put on a fearless face after the loss took some of the shine off the Americans' otherwise decisive 3-1 win that booked their place in the next round against France in April.
Williams' last title was at the 2016 Australian Open before she took time away from the circuit to give birth to her little girl.
Williams said: "This is literally my first time travelling with the baby and everything".
Serena was scheduled to compete in the Australian Open this January, but made a decision to pull out after losing an exhibition match in December.
"I didn't expect to have that much power on my serves, even though they didn't go in". I've broken down I don't know how many times.
Williams, who was playing doubles with her sister, Venus Williams, also shared a video tweet zooming in on the baby, who was wearing a red and white headband.