The actor watched his son struggle with alcohol and marijuana abuse as a teen, and then deal methamphetamines in his 20s.
His drug dramas landed Cameron behind bars for over six years, during which time he confessed to smuggling illegal substances into jail.
He was released to a half-way house in July 2016, but tested positive for marijuana - a violation of the terms of his parole - a few months later.
Now that Cameron is clean and sober, his dad admits he's glad he has turned his life around, because there was a period where he feared every phone call would be someone informing him his son had died.
"There were moments when hope dwindled... and then it's just a train out of the station," the "Ant-Man" star tells People magazine. "Life became a series of crises. I thought I was going to lose him."
Cameron has detailed his struggles with addiction in his new memoir "Long Way Home", revealing he now works hard to maintain his sobriety.
"I hated the wreckage I saw in my life because of drugs, but I just couldn’t stop," he shares, admitting he hopes his story helps other addicts "seek help."
The 40-year-old is also now a family man, raising his 22-month-old daughter Lua with longtime girlfriend Viviane Thiebes.
He has been sober since June 2018.