Restless Legs Syndrome (RLS) is a sensory-motor neurological disorder that overallyaffects about 10 percent of adults. RLS can be correlated with opioid abuse relapse and considered as a risk factor in relapse of opioid abuse . This study aimedto investigate the relationship between restless legs syndrome and opioid use relapse.In this crosssectional study participants included 214 patients with opioid abuse referred to Tehran Psychiatric Institute for substance abuse treatment in 2015.After obtaining informed consent from patients, Restless Legs Syndrome Rating Scale appliedto assess Restless Legs Syndrome severity.To determine relapse of substance abuse urine morphin test was used.The results showed that there was no significant difference statistically between patients with substance abuse relapse and patients without substance abuse relapse in terms of sex, marital status and education level (p> .05) while there was significant difference between the two groups in terms of age, the age of onset of drug use, way of drug consumption, family history of drug abuse and smoking (p <.05). Three month after the withdrawal the frequencies of mild and sever cases of RLS in group without substance abuse relapse were 66.7% and 1.3% respectively while in group with substance abuse relapse the frequency of mild and sever cases of RLS were 22.8% and 19.9% respectively which statistically was meaningful(p = .0001).Based on the findings of this study there was a correlation between RLS and substance abuse relapse in abusers who experienced substance withdrawal. As well as increasing the time from withdrawal the severity of this syndrome will increase.