Rumination is thought to play a central role in affective disorders such as social anxiety disorder (SAD). Past research indicates that rumination tends to exacerbate negative emotions and increase the risk of engaging in maladaptive coping behaviors (e.g., avoiding social activities). However, little is known on how to effectively protect against the negative outcomes of rumination. Previously, Zaki, Coifman, Rafaeli, Berenson, and Downey (2013) found that negative emotion differentiation (NED) protected against rumination and nonsuicidal self-injury in borderline personality disorder. Nevertheless, it is unclear whether this protective effect would extend to other populations and behaviors. Therefore, the present investigation sought to replicate and extend Zaki et al.'s (2013) findings in the context of SAD. In two studies, we examined if NED would moderate the positive association between rumination and frequency of social avoidance. Study 1 involved 29 individuals who met criteria for SAD with or without co-occurring major depressive episode, while Study 2 involved a nonclinical sample of 190 college students. All participants completed a measure of rumination and an experience-sampling diary which provided indices of NED and social avoidance. The results from both studies were unanimous: NED significantly moderated the relationship between rumination and social avoidance such that the positive association between rumination and social avoidance was significant for low but not moderate to high NED. Overall, the findings provide a conceptual replication of Zaki et al. (2013) and further evidence for the protective effects of NED against the maladaptive behavioral consequences of rumination across populations.