The Coronation Street star, 29, shared the happy news on Friday (15 January) with her 180,000 Twitter followers.
In a sweet message to her social media family, Paula said: "News just in... The new addition to the Shaw clan will be arriving summer time and @SirTomShaw and I are thrilled! #doubletrouble."
Awwww - congrats!
The actress - who plays Kylie Platt in the ITV soap - welcomed her first child with husband Tom on New Year's Eve 2014.
Arthur-Wallace turned one just two weeks ago.
Paula and long-term partner Tom married in May 2014 at Leeds Cathedral. A month later, she announced she was pregnant with her first child.
Fans and celeb pals have been congratulating Paula on her good news, including former co-star Michelle Keegan.
She tweeted: "Arghhhhhhhhh oh my god! Amazing news congratulations to both of you!!! So exciting xxxxxxxx."
Meanwhile, fellow Corrie mummy Catherine Tyldesley said: "Wahoooooo!!!! So giddy for you!!! Big love xxxx."
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