Douglas made the remarks in an interview that aired Monday on NBC's "Today."
"Look, my son was a drug dealer and he's been trying to kill himself for a while and I can't condone his behavior, so I think the court recognized his drug addiction as well as the crime that he committed," Douglas told "Today" anchor Matt Lauer. "And it's an adequate, I think, amount of time for anybody to spend in jail, and the best part of it is, he will be able to start his life afresh."
Cameron Douglas, 31, pleaded guilty in January to conspiring to distribute drugs. He was sentenced last month.
Michael Douglas admitted he and his ex-wife Diandra are partially to blame for their son's troubles.
"I've taken blame about being a bad father -- if being a bad father is working your butt off trying to create a career at one time," the actor told "Today."
"I've also confessed the fact that I was in rehab 20 years ago. So we had that issue and as far as his mother was concerned, she was a very young mother when she had Cameron and her skills were limited to such an extent. The other part, of course, is genes. I lost a brother with an overdose four years ago. I have another brother who has been on the program for years. My ex-wife's family has alcoholism running in it, so you have that part and then you finally end up with who you choose to hang out with. In Cameron's position, he took a lot of lowlifes and he was a very attractive target to hang out with and I don't think that helped, either."