The 30-year-old radio and television presenter made the announcement on her blog in a post entitled 'Some lovely news...'.
Cotton said: "Jesse and I are very happy to announce we are having a baby.
"We are over the moon, morning sickness aside (me, not Jess) and looking forward to the little Cotton Woods arrival."
Cotton began dating musician/model Jesse - Ronnie Wood's son - in June of last year.
The pair began their relationship shortly after the BBC Radio 1 DJ broke off her engagement with former fiancé Jesse Jenkins.
Watch a clip of Fearne Cotton carrying the Olympic Torch below: