The Paper Moon star is allegedly seeking professional treatment at an undisclosed location after suffering a setback in her sobriety.
A source tells RadarOnline.com, "Tatum made the decision to voluntarily check into rehab after having a relapse about a month ago when she began using cocaine again."
O'Neal, 48, has a long history of substance abuse, but she insisted she had kicked her habit once and for all after her 2008 arrest for cocaine possession. She pleaded guilty to the misdemeanour charge and was ordered to complete two sessions in a drug treatment programme.
The daughter of actor Ryan O'Neal even served as her embattled half-brother Redmond's sober buddy in 2010 to help him get clean after multiple drug arrests. In October (11), he was spared jail and ordered to return to a treatment centre after he confessed to using drugs while in rehab.