The purpose of the study was to investigate the effects of alcohol drinking of employee on job engagement and interpersonal conflict at work. In order for a better understanding of the effects, we distinguished drinking based on whom they drank with: work-related vs. non-work related. Based on self-control strength theory(Baumeister, Vohs, & Tice, 2007) and effort-recovery model(Meijman & Mulder, 1998), we hypothesized that self-control plays a key role in the process by which work-related drinking influences job engagement and interpersonal conflict. Multi-level analyses on daily survey data from a total of 367 employees for two weeks showed that as participants drank more alcohol with work-related person(s), the level of ego-depletion got worse, and as a result, job engagement faltered. As for interpersonal conflict, the effects of work-related alcohol consumption and ego-depletion varied according to the level of trait self-control. On the other hand, non-work related drinking was positively related to ego-depletion, which was related to only interpersonal but to job engagement. Theoretical and practical implications of the findings and future research directions were discussed.