We develop a dyadic model of social exchange at work and shed light on how employees exchange support on a daily basis. In addition, we investigate when providing support relates to the work engagement of the provider. We hypothesized that the provider repeats his or her supportive action within a day when the receiver also provides support or when the receiver is engaged. We also predicted that supporting a coworker relates positively with the provider's engagement and that this relationship is strengthened when the support is given to an engaged receiver. To test our hypotheses, we used experience sampling and investigated support provision and work engagement in dyads of coworkers during the morning and afternoon of 4 working days. Multilevel analyses based on 123 dyads (N = 418-692 data points) revealed that supporting a coworker relates positively to the supporter's engagement and that this relationship is stronger when the support is given to an engaged receiver. Furthermore, results showed that the provider is more likely to repeat his/her supportive action if the receiver also provides support. We did not find a moderation effect of the receiver's engagement on the link between support provision during the morning and support provision during the afternoon. Altogether, our study provides insight on what motivates employees to support their coworkers and when providing support is most engaging. Furthermore, we show that the behavioral assumption of social exchange theory (i.e., reinvesting support in a receiver who reciprocates) exists within a daily work context. (PsycInfo Database Record (c) 2020 APA, all rights reserved).