The singer made the surprise announcement and showed off her baby bump on the red carpet at the MTV Video Music Awards.
Wearing a long orange gown by Lanvin, the 29-year-old clutched her visible bump and told assembled press: 'I have a surprise!'
Arriving onstage in a purple glittery blazer and black trousers by Dolce & Gabbana, the pregnant star said: 'I want you to feel the love that's growing inside of me.'
The singer didn't let her pregnancy prevent her from an energetic performance of Love On Top, attracting a standing ovation from the audience.
During the performance Beyoncé ripped open her jacket and proudly rubbed her baby bump.
The cameras panned to the audience where husband Jay-Z was beaming, as his friend Kanye West jumped up and down, smacking the father-to-be on the back and shaking him.
Beyoncé, who has won 16 Grammy awards and headlined this summer's Glastonbury Festival, hinted in a recent interview with Piers Morgan that her priorities might change from career to motherhood soon.
Beyonce steals the show with her performance and baby news - watch the video