The pregnant star dressed her growing belly in a chic black dress and silk floral robe as she watched Venus battle Elisa Mertens of Belgium during the Women's Singles round three match on Philippe-Chatrier Court at Roland Garros.
Serena accessorized her look with a headband and stylish sunglasses.
"I think the surprise of knowing what you are going to have on that very special day you give birth is prob the best surprise you can ever have!" she wrote on Instagram. "So to clarify what Venus said, I am always joking with my sisters to see what favors I can get them to do for me next. If I want something from one of my sisters, I say, 'Baby Venus,' Baby Lyn,' or 'Baby Isha' needs it."
"I did not grow up with brothers, only sisters and we all say 'she' more than 'he.' Unless I'm joking with my dad or Alexis and I'm trying to con something out of them too," Serena added. "Hey, I'm the youngest of five. I've always tricked all of them, what can I say!"