"I suffered my stroke in 2002, but it is now yet again, that I draw upon the many adults and young children I've met throughout my life who courageously fought and usually lost in their battles against this deadly disease," Hart wrote on his Facebook page Monday.
The former pro wrestler thanked his wife, children and grandchildren for their support, and says he'll fight with every bit of strength he has left.
"Love is my weapon and I've got much of it around me all the time, for which I'm truly blessed and eternally grateful," Hart says.
Hart is a five-time WWE World Heavyweight Champion and was inducted into the WWE Hall of Fame in 2006.
"WWE extends its support to Bret and his family in his fight with prostate cancer," WWE wrote on its website.
Many WWE legends and current stars expressed their thoughts and prayers to the 'Hit Man' on social message.
Current WWE Champion Triple H tweeted, "Thoughts and prayers with @BretHart and his family. Let's all get in his corner to help him win this fight!!! #GetWellHitman."
Superstar Roman Reigns said, "Everyone gets knocked down...but the BEST get through it. Prayers are with @BretHart ... We're all with you. #GetWellHitman"
Bret Hart's niece, Natalie "Nattie" Neidhart, wrote on Instagram, "I'm so proud of @brethitmanhart for coming forward about his battle with cancer and using his voice to help others. I know it's taken a lot of courage for Bret to share this, but now his voice is a powerful tool that can help inspire the masses. If anyone can beat this, it's Bret."
Neidhart ended her message to her uncle by quoting Bret's signature slogan of "Best there is. Best there was. Best there ever will be."