"I'm just happy to win a match here, " Williams told the crowd in Court Philippe Chatrier.
The fashion statement, this time in the form of a black bodysuit with a red belt that she said made her feel like a "warrior princess".
She said: "I don't know".
The three-time French Open champion came in unseeded despite being ranked No. 1 in the world when she took maternity leave a year ago, later giving birth to her first child in September.
Serena Williams attended the recent royal wedding of Prince Harry and Meghan Markle rather than play in the Italian Open, an important clay-court tuneup for the French Open. "Can she do it?"
Serena Williams plays a forehand during her first round match against Kristyna Pliskova of Czech Republic at the 2018 French Open on May 29, 2018 in Paris.
Tuesday marked Williams' first appearance in a majors match since she won the 2017 Australian Open while in the early stages of her pregnancy.
"She's a genuine champion", Barty said. She who won four of seven matches that were all played when Serena was a teenager. And just coming back from the physical [side] of having a baby, at my age, is never really easy.
Which means she is up against Australian 17th seed Ashleigh Barty in the second round.
Whatever happens over the next two weeks, Williams insists her family priorities have eased the expectations on her as a player. She was clearly missing the weight of shot against the 70th ranked Pliskova, running after, rather than calling the shots.
Two-time French Open champion Maria Sharapova of Russian Federation was pushed to three sets in her return to this event following a two-year absence.
She had deliberately held back from a return, skipping Rome and Madrid, in order to make sure she was ready to compete on what is her least natural surface, training at the academy belonging to her coach, Patrick Mouratoglou. "I'm not putting any pressure on myself as I normally do", Williams began, before continuing after a pause and a laugh.
She said the outfit also had some functionality. "It was a wonderful experience and it just kind of helped me get everything going and get my competition and competitive juices flowing", said Serena. She defeated Steffi Graf who defeated Chris Evert who defeated Billie Jean King, Rosie Casals and pretty much everybody of effect from the early days of professional women's tennis.
Pliskova made the ideal start in the tiebreak, building up a 3-0 lead, but Serena clinched six points in a row, and finally closed out the tiebreak after Pliskova sailed a backhand long.In the second Serena, who completed her first win of the season against a lefty player, the 168th in her career on clay, twice gave a break back to the Czech who started to play flatter and deeper down the line forehands in the second set.