The Magnum, PI actor, 63, was apparently convinced to take part by former contestant Steve Guttenberg, his co-star in 1987 movie Three Men And A Baby and its sequel.
A source told the National Enquirer: "Executives wanted an older hunk to bring in the baby boomer audience. Tom is incredibly popular with women 40 through 65, and producers were ecstatic when, at Steve's urging, he expressed interest in competing on the show."
Singer Toni Braxton and former 'N Sync star Lance Bass are also rumoured to be taking part. The official list of competitors will be released on August 25.
The seventh season of the dance contest kicks off in the US on September 22.