This paper focuses on the interrelationships between the different dimensions of supply chain integration. Specifically, it examines the relationship between employee commitment and supply chain integration dimensions to explain several performance measures (flexibility, delivery, quality, inventory and customer satisfaction). Very little research has been conducted into this topic, since employee commitment is rarely included as an antecedent of the effect of supply chain integration on performance. Seven research models have been analysed with Structural Equation Models using a multiple-informant international sample of 266 mid-to-large-size manufacturing plants. The findings suggest that the relationship between employee commitment and operational performance is fully mediated by supply chain integration. Employee commitment contributes to improving internal integration, and internal integration affects performance both directly and indirectly. Moreover, obtaining internal integration helps to achieve supplier and customer integration. As a result, companies should strive to achieve both employee commitment and internal integration, as they mutually reinforce each other. Similarly, managers should achieve internal integration before external integration and include external integration at the strategic level in order to reap the greatest advantages from supply chain integration. Meanwhile, managers should promote employee commitment not only for better supply chain success, but also to mitigate the barriers of supply chain management implementation.