<p>Existing theory on capitalization (i.e., sharing positive events with others) positions disclosers of positive events as the sole drivers of capitalization, with responders as passive targets of capitalization. However, given that capitalization can in principle only transpire with a responder, it is reasonable to expect that responders also play important upstream roles regarding whether capitalization transpires. Drawing from Emotion as Social Information (EASI) theory, we examine how and when coworker displayed happiness elicits focal employee workplace interpersonal capitalization. Via a preregistered experiment, a three-wave round robin field study, and an experience sampling field study, we found support for our predictions that coworker displayed happiness evokes employee workplace interpersonal capitalization through both an affective reaction mechanism (employees’ own experienced happiness) and an inferential mechanism (anticipated coworker responsiveness). Further, we found support for our hypothesis that the strength of coworker friendship acts as a key social-relational boundary condition that weakens both mediating pathways, suggesting that the affective reaction and inferential mechanisms are more efficacious when coworker friendship is weaker. Overall, we offer a consensus shifting contribution by elucidating how the responder fulfills a much larger role regarding antecedent factors of capitalization than currently constituted.</p>