O'Neal, 69, was arrested in 2008 for alleged methamphetamine possession.
"He did successfully complete his diversion program and the case was dismissed today," Jane Robison, spokeswoman for the Los Angeles District Attorney's Office, told E! News Friday.
The "Paper Moon" and "Love Story" star marked the first anniversary of his longtime love Farrah Fawcett's death last month.
He and Fawcett are the parents of Redmond O'Neal, who has long battled an addiction to drugs, but is now living in a sober-living facility.