["Scandinavian Journal of Psychology, Volume 67, Issue 2, Page 547-557, April 2026. ", "\nABSTRACT\nThe relation between sleep and irritable affect has been studied extensively. However, whether this relation is bidirectional remains unclear. Furthermore, less is still known about associations between sleep and interpersonal behaviors and perceptions during social interactions. The current study examined bidirectional within‐person relations between actigraphy‐based sleep, and irritable affect, quarrelsome behavior, and agreeable perceptions of others assessed using event‐contingent recording of social interactions in a sample of n = 50 participants during either 20 or 40 days. We found that after a night of worse sleep than usual, participants reported more anger and frustration the next day (−0.12, p ≤ 0.01). The reverse was not found. There were no direct associations between sleep and quarrelsome behavior or between sleep and agreeable perceptions. However, worse sleep than usual was indirectly related to more quarrelsome behavior (−0.05, p ≤ 0.001) and less agreeable perceptions (0.06, p ≤ 0.001); that is, via increased irritable affect. These mediation effects imply that poor sleep may impair the quality of one's social interactions. Therefore, targeting sleep could be a means to improve personal and professional relationships.\n"]