Speaking to You magazine, Springwatch host Michaela spoke of her emotion at being advised to have the operation following her cancer diagnosis.
"The tears started to roll as my doctor tried to tell me what would happen next," she said. "But I only took in every fifth word or so. The one word that registered was 'cancer'.
"I couldn't get my head around the fact that on Monday morning I'd been apparently healthy, by Tuesday I had cancer, and by Wednesday I was talking about a double mastectomy."
The 48-year-old mother-of-three, who plans to have reconstructive surgery, is now dedicated to encouraging other women to have routine check-ups and mammograms.
"If I'd put mine off," she said. "My story could have been a very different one."
Michaela took part in diving show Splash! in February 2014
On Sunday Michaela also revealed that is now working alongside Breakthrough Breast Cancer – the UK's leading charity devoted to fighting the disease.
"Today I become an ambassador for @BreakthroughBC to encourage women to have regular mamograms," she tweeted. "This year has been a challenging one. In Feb I was diagnosed with breast cancer. I was lucky, I found it early."