Literature on organizational learning (OL) shows that even firms who self-perceive themselves to have appropriate organizational structures still fail to generate appropriate learning outcomes. In this article, we claim that one of the neglected key factors explaining learning failures are organizational defensive routines (ODRs). Drawing on the literature, our theoretical inference is that high levels of ODRs can negatively moderate the relationship between organizational structures and OL. To test this moderation hypothesis, the study employs hierarchical regression analysis on a sample of 358 respondents from various industries in the United Kingdom. The result confirms that formalization negatively affects OL, and the effect of formalization on OL is negatively moderated by ODRs regardless of organizational age, size, and sector.