Dating apps may potentially serve as an environment that subjects young women to the harmful effects of appearance-related pressure. The current study assessed for the first time whether women's dating app use predicted body dissatisfaction (BD), urges to engage in disordered eating (DE), and negative mood in daily life. We also examined the unique effects of women's dating app partner preferences (i.e., seeking idealised versus non-idealised physical characteristics) on the aforementioned outcomes, and whether appearance-based rejection sensitivity (appearance-RS) moderated the effects of dating app use. Participants (N = 296; 100% women) first completed a baseline survey assessing lifetime dating app usage (i.e., current or former usage), partner preferences, and appearance-RS, followed by a 7-day smartphone-facilitated ecological investigation into momentary experiences of BD, DE urges (i.e., binge-eating/purging, dietary restraint, and exercise), and negative mood. Ninety-four women (32%) reported lifetime dating app usage, which, relative to non-use, predicted greater daily urges for binge-eating/purging and negative mood. However, appearance-RS failed to moderate these effects. Among dating app users, partner preferences were not a significant predictor of the central outcomes. These findings extend previous research by examining the unique effects of dating app use on everyday BD, DE urges, and negative mood. Replication and extension are encouraged.