Coworker capitalization refers to employees sharing work-related positive events with their coworkers (Watkins, 2021). Existing research suggests that individuals can benefit from sharing positive events with those in close relationships. However, this phenomenon may not hold true when it comes to sharing such events in coworker relationships. Unlike close relationships, coworker relationships involve more unknowns, leading recipients to form diverse interpretations regarding why their coworkers share work-related positive events with them. To shed light on this, I introduce attribution theory (Heider, 1958) as a novel perspective to understand the effects of coworker capitalization. I propose that coworker capitalization may prompt recipients to attribute three distinct motives to disclosers: a self-promotion motive, another performance promotion motive, and an expressing positive affect motive. These attributed motives serve to explain why coworker capitalization may or may not result in benefits for disclosers. More specifically, attributing coworker capitalization to the discloser’s self-promotion motive may explain why recipients engage in social undermining behaviors toward the discloser. In contrast, attributions of other performance promotion may explain why coworker capitalization can benefit the discloser: recipients may engage in interpersonal citizenship behaviors toward the discloser with such an attribution. Finally, attributing coworker capitalization to the discloser’s expressing positive affect motive can explain why recipients are constructively responsive to the discloser. Drawing from attribution theory, I also propose that recipients’ preexisting impression about the discloser’s narcissism may moderate how they attribute motives to their coworkers’ capitalizing behaviors. I found preliminary support for this hypothesized model through a quasi-experimental experience sampling study. Implications and limitations are discussed.