Beyoncé, who already has a five-year-old daughter named Blue Ivy, revealed in the joint post with her husband Jay Z: "We are incredibly grateful that our family will be growing by two. We thank you for your well wishes."
The 35-year-old also uploaded onto Instagram a photo of herself with a huge baby bump, but did not reveal a due date for the twins.
The announcement will come as a big surprise to Beyoncé's fans considering that she is due to perform at the Coachella music festival in California this coming April.
Beyoncé announced her first pregnancy in dramatic fashion live on the MTV Music Awards back in 2011 . During the performance, she declared: "I want you to feel the love that's growing inside of me." And then near the end of the song, she unbuttoned her tuxedo jacket to reveal her baby bump.
In a documentary released in 2013, Beyoncé said she loved the experience of being pregnant. "Being pregnant was very much like falling in love. You are so open. You are so overjoyed. There's no words that can express having a baby growing inside of you, so of course you want to scream it out and tell everyone," she said.
Jaz Z revealed in the lyrics of his song 'Glory' that Beyoncé sadly suffered a miscarriage before the birth of their child.
Speaking about the miscarriage in the HBO documentary entitled 'Life Is But a Dream', Beyoncé revealed, "I flew back to New York to get my check up - and no heartbeat. Literally the week before I went to the doctor, everything was fine, but there was no heartbeat."
She added, "I picked out names. I envisioned what my child would look like . . . I was feeling very maternal."
She also discussed how the power of music helped her in those dark days. "I went into the studio and wrote the saddest song I've ever written in my life," she stated. "It was the best form of therapy for me, because it was the saddest thing I've ever been through."