The presenter, who gave birth to her third child Chester a year ago, has reflected on how quickly time has passed.
On the morning of Chester's birthday, she tweeted: "Happy 1st birthday to our gorgeously perfect wonderfully beautiful Chester... Where did that year go?"
Willoughby, 34, has two other children - Harry, six, and Belle, four, - with husband Dan Baldwin.
Happy 1st birthday to our gorgeously perfect wonderfully beautiful Chester... Where did that year go?!!! pic.twitter.com/MHczGvIo3h— Holly Willoughby (@hollywills) September 29, 2015
Willoughby, who rarely shares photos of her children, uploaded an adorable photo holding Chester's hand, which was neatly laid on her palm.
Within minutes she had received thousands of happy birthday messages for her son from her 6.13 million fans on Twitter.
They too, seemed to comment on how quickly the year has gone since she gave birth.
@hollywills That year has flown by. Happy 1st birthday, Chester! X— Laura Jean Smith (@LauraJean1992) September 29, 2015
@hollywills awwww happy birthday little Chester! That's gone so quick! Can remember when you and our Sam Bailey was due around the same time— MEL_14Days & 21Days (@Storm_Diva_Army) September 29, 2015
@hollywills quickest year ever!! Happy birthday Chester🎉 hope you have a beautiful day💗💗— bethanyy (@bethanyyjuliexo) September 29, 2015
Willoughby announced recently in an interview that she doesn't want any more children.
Speaking to The Sun, she said: "We keep having babies. But I am done now. I am not going anywhere."