The application of ecological momentary assessment (EMA) in community settings provides a powerful opportunity to obtain measures of emotional reactivity to daily life events, as well as emotional dynamics in real time. This investigation examines the association between emotional reactivity to daily events and emotional experience in mood and anxiety disorders in a large community-based sample. Two-hundred and 87 participants with a lifetime history of bipolar I disorder (BPI; n = 33), bipolar II disorder (BPII; n = 37), major depression (MDD; n = 116), anxiety disorders without a mood disorder (ANX; n = 36), and controls without a lifetime history of mood, anxiety, or substance use disorder (n = 65) completed a 2-week EMA evaluation period concerning mood states and daily events. Following positive events, individuals with BPI reported greater decreases in both sad and anxious mood than did controls, and individuals with MDD experienced greater decreases in anxious mood. Following negative events, the BPII, MDD, and ANX (but not BPI) groups experienced greater increases in anxious mood, with no group differences in sad mood. Greater variability and instability were observed for sad mood in the BPII and MDD groups, and greater variability and instability was observed for anxious mood in all of the mood/anxiety groups. However, no group differences were observed for the inertia of sad or anxious moods. The findings demonstrate differences in emotional reactivity to daily events as well as the general affective dynamics of emotional states among individuals with mood or anxiety disorders, with potential specificity for BPI disorder relative to other disorders. Emotional variability and instability may constitute a nonspecific characteristic of both mood and anxiety disorders.