Disordered sleep has been linked to impaired emotional functioning in healthy and depressed individuals. Little is known, however, about how chronic sleep problems influence emotional reactivity in everyday life. Participants with major or minor unipolar depressive disorder (n = 60) and healthy controls (n = 35) reported on sleep and emotional responses to daily life events using a computerised Experience Sampling Method. We examined whether impaired sleep quality influenced emotional reactivity to daily events, and if this relationship was altered by unipolar mood disorders. Among healthy individuals, sleep difficulties were associated with enhanced negative affect (NA) to unpleasant events and a dulled response to neutral events. However, among mood-disordered persons, sleep difficulties were associated with higher NA across all types of everyday life events. Impaired sleep quality differentially affects daily life emotional reactions as a function of depression.