Serena Williams told her daughter that she is going to be a big sister in an adorable Youtube video posted to her channel on Tuesday.

The 41-year-old tennis superstar — who revealed she is pregnant with her second child on the Met Gala red carpet earlier this month — documented the moment she told Olympia, five, the happy news.

The clip, titled 'Olympia's Surprise', started out with Serena showing the camera a close-up of a positive pregnancy test, revealing she was 'super happy.'

Serena then recalled a funny anecdote as she told the camera that Olympia did not know she was pregnant yet, but did call her 'fat' and was 'stressed out' by her weight gain.

Later in the video the athlete was joined by her husband Alexis Ohanian, 40, as they broke the news to the little girl, who was overjoyed and began running and shrieking in excitement.