The star of Zoolander was diagnosed with a tumour in 2014.
He says he now wants to share his story to lend his support for a controversial test which saved his life.
In an article on Medium, Stiller described the moment of his diagnosis as "a classic Walter White moment, except I was me, and no-one was filming anything at all".
He wrote: "I got diagnosed with prostate cancer Friday, June 13 2014. On September 17 of that year I got a test back telling me I was cancer free.
