[4] Through his biological father, Cain is partly of Japanese descent, with the rest of his ancestry being Welsh, Irish and French Canadian.

Soon after Dean's birth, his mother, pursuing an acting career, moved him and his older brother Roger to Los Angeles.

Among his schoolmates were Charlie Sheen, who played on the same baseball team as Cain when they were children, as well as Rob Lowe and his brother, Chad.

His senior thesis was titled "The History and Development of the Functions of the Academy of Motion Picture Arts and Sciences".

[9] After graduating, Cain signed on as a free agent with the NFL's Buffalo Bills, but a knee injury during training camp ended his football career prematurely.

[10] With little hope of returning to sports, Cain turned to screenwriting and then acting, shooting dozens of commercials including a volleyball-themed spot for Kellogg's Frosted Flakes and appearing on popular television shows like Grapevine, A Different World, and Beverly Hills, 90210.

Cain later made his first return to the Superman franchise with a special guest role in a season seven episode of Smallville as the immortal Dr. Curtis Knox, a character based upon the DC Comics villain Vandal Savage;[11][12] Cain returned to the Superman universe again between 2015 and 2017, in a recurring role on Supergirl, as the title character's foster father, Jeremiah Danvers.

[13] In 1998, Cain started the Angry Dragon Entertainment production company, which produced the TBS Superstation television series Ripley's Believe It or Not!

He has also starred in several films, including The Broken Hearts Club (2000), Rat Race (2001), Out of Time (2003), and Bailey's Billion$ (2004).

[14] Cain was a contestant in an NBC celebrity reality competition series called Stars Earn Stripes.

In 2016, Cain played a guest role on the Netflix original series Lady Dynamite as Graham the ex-fiancé of Maria Bamford.

[26] He has a son named Christopher Dean Cain (born June 11, 2000) with ex-girlfriend and Playboy Playmate and Spanish model Samantha Torres.