The former X Factor and America's Got Talent judge said that she underwent the operation after finding out that she has a gene which increases the risk of breast cancer.
"As soon as I found out I had the breast cancer gene, I thought, 'The odds are not in my favour'," she told Hello! magazine.
"I've had cancer before and didn't want to live under that cloud. I decided to take everything off and had a double mastectomy. For me, it was a no-brainer."
Osbourne - who successfully fought colon cancer in 2002 - added that she didn't want to be pitied, saying that having the mastectomy was "a decision I made that's got rid of this weight that I was carrying around".
The Talk co-host explained: "I want to be around a long time and be a grandmother to Pearl. I didn't even think of my breasts in a nostalgic way, I just wanted to live without that fear."
Osbourne's granddaughter Pearl was born earlier this year to parents Jack Osbourne and Lisa Stelly.