Objectives: The present study was carried out with the purpose of investigating lifetime non-fatal overdose of illicit addictive substances, its relationship with demographic characteristics, and pattern of abuse in individuals with substance dependency. Method: In a descriptive study, data were gathered from 29 provinces in Iran from May to September 2008. Addicted individuals were interviewed in prisons, treatment centers, and on the streets. Selection of participants was random in prisons and treatment centers, and via snowball sampling on the streets. Results: 3329 (42.1%) of individuals with dependency on illicit addictive substances, reported experiencing overdose in their lifetime. Lifetime experience due to non-fatal overdose in Iranian drug users was significantly higher in those whose primary substance was Norjesik (53.9% vs. 41.6%, p<0.001) or Heroin  (50.2% vs. 40.1%, p<0.001), and intravenous drug users (56.1% vs. 38.8%, p<0.001). Logestic regression showed that gender (p<0.01), living alone (p<0.05), unemployment (p<0.05), illegal income (p<0.01), history of  cigarette use in one family member (p<0.001) were predictors of experiencing non-fatal overdose. Conclusion: Paying attention to non-fatal substance overdoses in addicts in general, and heroin, Norjesik and intravenous users in particular is crucial. Organizaitons active in prevention, treatment and harm reduction should make the necessary preparations.