The 29-year-old star confirmed her pregnancy at the MTV Video Music Awards. She posed for photos with her hands cradling her baby bump and said: "I have a surprise!"
Her representative also told people.com: "I'm happy to say it's true."
Beyonce and Jay Z have been married for three years.
"They told friends last month. She's never been happier. Seriously it's all she's been waiting for. And Jay is like an excited kid. They're adorable," a source said.