Evidence suggests that both dissociation and negative affect (NA) may precipitate binge eating. The extent to which dissociation may impact the experience of NA around binge eating is unclear. Women with bulimia nervosa completed a 2-week ecological momentary assessment protocol of dissociation, NA, and binge eating. Multilevel modeling was used to examine dissociation as a moderator of NA before and after binge eating. NA was greater at the time of binge eating for participants higher in average dissociation (between subjects) and when momentary dissociation was greater than one's average (within subjects). The trajectory of NA was characterized by a sharper increase before binge eating for participants higher in average dissociation; the NA trajectories were characterized by sharper increases before and decreases after binge eating when momentary dissociation was greater than one's average. Results support the salience of both dissociation and NA in relation to the occurrence of binge eating.