The Cambodian conflict (1979 - 1991) became the dominant issue in international relations of Southeast Asia after the end of Vietnam War. The paper aims to clarify how the Cambodian problem impacted on changes of Vietnam - ASEAN relations in the last decades of the 20th century. These countries accused Vietnam of invading Cambodia, causing regional instability, therefore stagnating the rapprochement with Vietnam. However, two sides’ proactiveness in successfully dealing with Cambodia’s political conflicts contributed to recover regional relations and to rapidly promote Vietnam’s integration in ASEAN in 1995.