Williams was romantically linked with rapper, Common until the two broke-up in 2010. In 2016, she became engaged to co-founder of Reddit, Alexis Ohanian. In September 2017, she gave birth to a beautiful baby girl, whom she named Alexis Olympia Ohanian Jr. In November 2017, Williams and her man, Alexis Ohanian got married.
The star-studded wedding festivities were held at New Orleans Contemporary Arts Center. Beyoncé, Kim Kardashian, Eva Longoria, and Ciara were in attendance. Williams is also very close to her sister, Venus. She has often cited her sister as being her inspiration to keep playing tennis.