The study attempted to fill a gap in the research on international business by providing fresh evidence of the effect of the degree of internationalization on firm performance and the influence of organizational slack on this relationship. By applying a fixed-effects model to data from 569,767 Vietnamese enterprises from 2007 to 2015, a significant W-shaped linkage between internationalization and firm performance was revealed. Importantly, the results also emphasized the importance of three types of slack in the first stage of the internationalization process: absorbed slack human resources, other absorbed slack resources, and unabsorbed slack resources.

This paper aims to investigate the three-stage theory of international expansion in the long run from the perspective of firm behavior. Although this topic has been mostly explored using data from developed countries, this paper aims to fill the research gap in an emerging market by using an extensive unbalanced panel data of 12,704 unlisted Vietnam manufacturing enterprises from the General Statistics Office during 2007 to 2012. The findings illustrated a significant S-shaped relationship between internationalization and performance. Notably, the results depict significantly moderating effects of both high-discretion slacks and low-discretion slacks on the internationalization–performance relationship across three stages of global expansion as an enterprise enhances this relationship in the first and third stage although this worsens it in the middle stage. The empirical results suggest that firms should determine the optimum level of internationalization and slacks in addition to balancing their costs with their real gains.