The actress, who plays Linda Carter in the BBC One soap, announced her happy baby news via Twitter on Thursday afternoon (19 May).
Kellie said: "Shh… Don't tell anyone, but I'm pregnant! My hubby and I are over the moon & looking forward to meeting our little person in Nov #Mama @ 40."
She celebrates her 40th birthday in July.
Kellie also promised she'd be back to EastEnders after the birth: "And for those of you that want to know, I will be returning to@bbceastenders after I've had the baby #queenvicismyhome#LindaCarter4ever."
This will be Kellie and husband Paul's second child. They're already parents to son Freddy.
Kellie received a slew of congratulatory messages from fans and friends on Twitter, wishing her well and sharing their excitement at her happy news.
@kelliebright76 omg omg im screaming so so happy for you guys! Congratulations beautiful eek cant wait ! Love you so much. Stay blessed— Sαfα (@safalovekellieb) May 19, 2016
@kelliebright76 Oh my god! Congratulations! Such a lucky baba to be born into such love— Niki (@NikiNoox) May 19, 2016
@kelliebright76 omg!! Congratulations my fave,that baby will have the best mummy,daddy and brother ever— Codie (@TeamEECarter) May 19, 2016
@kelliebright76 OMG! Congrats Kel! So happy for you and Paul and ofcourse little Fred! So excited for you all!— KBS (@kellie_fans) May 19, 2016
@kelliebright76 oh my goodness, congratulations!!!!!! So happy for you!!!— Kira (@kellieandannie) May 19, 2016
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