Objective: The purpose of the present study was to investigating the moderating role of the locus of control on the relationship between avoidance and anxiety attachment to parent and the tendency to drug use. Method: The research was correlational. The study population included all Shahid Beheshti University students of Tehran during 2018-2019. 253 students were selected using convenience sampling method. The participants responded to Zargar’s Addiction Potential Scale, Experiences in Close Relationships Scale, and Rotter’s Locus of Control Scale. Results: The results indicate that avoidance and anxiety attachment to parent showed a positive relationship with external locus of control and drug use tendency. The moderation regression analysis results indicate that locus of control moderated the relationship between attachment to parent and drug use tendency. Conclusion: In general, locus of control can have a moderating role between attachment and drug use tendency.