The paper presents an explanation for cross-border marriage from the perspective of ethnic culture and its impacts on management of social development (a case study in the Vietnam-China and Vietnam-Laos border areas). The phenomenon of cross-border marriage takes place quite popularly in border areas, especially in the densely populated locations near the borderline. Since ethnic culture is always preserved via marriages and marriage-related relationships, it is less impacted by national territorial factors. In the current context of globalization and development, cross-border marriage results in new problems for social development management, particularly in border areas.