The EastEnders star, 32, and her fiancé Marc Humphreys are expecting their first child together she has confirmed.
In a tweet to her 309,000 Twitter followers on Friday night (12 February), the actress said: "Evening all... Time to let everybody know that @cameramarc and I are having a baby in the summer. The three musketeers become four."
Awwww - congratulations.
Evening all... Time to let everybody know that @cameramarc and I are having a baby in the summer. The three musketeers become four.— Natalie Cassidy (@Nat_Cassidy) February 12, 2016
Fellow EastEnders star and mummy-of-one Jacqueline Jossa shared her happiness on Twitter, writing: "@Nat_Cassidy @cameramarc ooooo gooodnessss I'm so happy for you both!! Amazing news!!"
Jamie Lomas and Maria Fowler were also among the celebs to congratulate Natalie on her super happy news.
Benidorm actress Denise Welch added: "Huge congratulations to @Nat_Cassidy and @cameramarc on their pregnancy!!!! So pleased xxx."
The couple laughed off reports they are expecting a boy, admitting it's "at least eight weeks before it's possible to work it out".
A baby's sex is usually determined at the 20-week scan, if the parents chose to find out.
Natalie has a daughter Eliza, five, with previous partner Adam Cottrell - a relationship she admits was abusive.
The Strictly and CBB star, who plays Sonia Fowler in long-running soap EastEnders, got engaged to cameraman Marc last October.
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