Cameron Douglas, 37, was sentenced to five years in prison on drug charges back in 2010, but was given additional time after he was caught smuggling drugs into a correctional facility.
He was initially scheduled to be released in 2018.
The "Wall Street" actor's son, himself an actor and DJ, had pleaded guilty to selling bulk quantities of methamphetamine and cocaine at Manhattan's upscale Hotel Gansevoort in 2009.
Cameron Douglas, the only child from his father's 22-year marriage to Diandra Douglas, has had a life riddled with legal trouble and addiction.
He was arrested in California on cocaine possession charges in 2007. He pleaded guilty to a lesser charge of disorderly conduct. Two years later, Cameron Douglas was evicted from his $4,200-a-month home after falling behind on the rent.
His release will be good news for his father, who expressed frustration in 2013 on not being able to see his son. During his Emmy Award acceptance speech for his role in "Behind the Candelabra," the actor said he didn't understand why if a prisoner is "not violent...they punish you."
"In my son's case, he has spent almost two years in solitary confinement, and right now I'm being told I cannot see him for two years. It's been over a year now, and I'm questioning the system," he continued. "Obviously, at first I was disappointed with my son, but I've reached a point now where I'm very disappointed with the system."