This paper investigates the impact of regional economic cooperation between Vietnam and its partners during the 2000-2015 period, focusing on the Greater Mekong Sub-region (GMS). Overall, the GMS represents a significant portion of Vietnam's trade portfolio. China is the dominant trading partner in the GMS, exhibiting strong influence over Vietnam's trade, especially its imports. However, using the gravity model of trade, we find that Vietnam has not benefited from GMS cooperation, as exemplified by its significant trade deficit, particularly with China. We further find that human capital enhancement and financial development are key factors to facilitate Vietnam's trade, and mitigate its trade deficit with other GMS member countries. To this end, this study provides some important policy implications for the Vietnamese government as well as policymakers in other countries, when trading with larger partners in the context of regional economic cooperation.