Federal Judge Richard Berman announced the sentence Tuesday after hearing Douglas, 31, apologize and admit that he had squandered a lot of opportunities to turn his life around.
The judge said earlier that he did not have confidence that Douglas would turn his back on drugs after pleading guilty in January to drug charges.
Last week, Berman denied a request from the defense team to keep the sentencing private and documents sealed.
The sentencing stems from Douglas guilty plea in January in connection with a July, 2009 arrest for dealing large amounts of methamphetamine and cocaine at the Hotel Gansevoort in the Meatpacking District.
The defense had also asked Berman to consider giving Douglas a sentence of three and a half years in prison instead of the mandatory 10 years.
Many of Douglas' famous family and friends including his father, stepmother actress Catherine Zeta-Jones, and grandfather, legendary actor Kirk Douglas, had all written letters pleading for Berman to give him a lighter sentence.
Michael Douglas wrote a five-page hand-written letter that after his two-hour a week in-person visits with Cameron at the Metropolitan Correctional Center for the past eight months, he maintains his son is "sober," reported the New York Post.
"I get to witness the wonderful young man he can be. He maintains his spirit, blames no one but himself, and recognizes his criminal activity began with his heroin use," reported the Post.