Although he was interested in drama in high school, his early jobs centered around sports. After attending Yale, the Philiadelphia native played professional football with his hometown's Frankford Yellow Jackets. That led to radio gigs as a sports announcer and news commentator.
He made his Broadway debut in 1935 in the short-lived Broadway play Double Dummy. Eleven years later, he was working in radio when Garson Kanin offered him the role of gruff scrap-metal tycoon Harry Brock in Born Yesterday. The play was a smash hit, running for 1642 performances over three years, and making stars of Douglas and his leading lady Judy Holliday.
Lead roles and key supporting ones quickly followed: he was a soft-hearted gangster in Love That Brute (1950); a police captain who works with Richard Widmark to prevent an epidemic in Panic in the Streets (1950); a fisherman involved with Barbara Stanwyck in Clash by Night (1952); and a businessman being blackmailed amid the corporate politics of Executive Suite (1954).
When Paul Douglas died of a heart attack at 52, he was being considered for the Fred MacMurray role in The Apartment (1960). He had just appeared in an episode of The Twilight Zone called "The Mighty Casey." When the episode was completed, Rod Serling noted that Douglas didn't look well. A few days later, Douglas died. Serling used his own money to reshoot the show with Jack Warden in the Douglas role.
Paul Douglas was married five times. He walked down the aisle with actress Jan Sterling in 1950; they were married at the time of his death.