The present study investigated short‐term effects of daily social exclusion at work on various indicators of sleep quality and tested the mediating role of work‐related worries using a time‐based diary study with ambulatory assessments of sleep quality. Ninety full‐time employees participated in a 2‐week data collection. Multilevel analyses revealed that daily workplace social exclusion and work‐related worries were positively related to sleep fragmentation in the following night. Daily social exclusion, however, was unrelated to sleep onset latency, sleep efficiency and self‐reported sleep quality. Moreover, worries did not mediate the effect of social exclusion at work on sleep fragmentation. Theoretical and practical implications of the results are discussed. Copyright © 2012 John Wiley & Sons, Ltd.