The former Lizzie McGuire star and husband Mike Comrie revealed that they are expecting a baby on the same day that they celebrated their first wedding anniversary over the weekend.
Posting on Duff's official website, they said: "Baby Makes Three!!! We are extremely happy and ready to start this new chapter of our lives."
Writing on her Twitter account following the announcement, the actress added: "Wow! I am just overwhelmed by all of the wonderful messages everyone is sending! Thank you so much! Big hugs!"
Duff's older sister Haylie was one of the many well-wishers who posted their congratulations on Twitter, writing: "Congrats to my sissy @HilaryDuff and my B.I.L Mike on their 1 year anniversary and the tiny new addition :)"
Fellow Disney star Ashley Tisdale also congratulated Duff and Comrie on her own Twitter feed, saying: "So excited for @HilaryDuff and Mike!"
Duff and Comrie began dating back in 2007 and tied the knot at a ceremony in Santa Barbara, California last summer.
