In the situation of shortened product life cycles, modular product design enables organizations to adapt to unanticipated changes in their environments. This study extends modular systems theory to manufacturing process design and posits that: (i) firms can design their manufacturing processes for the same product into either an integrated or modularized structure, thereby being agile in dynamic environments, and (ii) the effect of manufacturing process modularity on agility is complemented by information systems (IS) flexibility. Conceptually, this study explains how important the congruence between the IS and manufacturing processes is to achieving agility in manufacturing and seeks to demonstrate how an IS adapts to shape agility. For practice, this study suggests that firms should focus their efforts on both IS flexibility and manufacturing process modularity, as well as their harmonization, in addition to modular product design.