We studied the mediating role of enjoyment in the relationship between task characteristics and work effort. To this end, an experience sampling study was implemented in which 50 employees reported on the characteristics of the task they were performing, their level of enjoyment, and their level of work effort five times a day for five working days. Results revealed that, at the concurrent level, task characteristics related to changes in task enjoyment, and that these changes were related to changes in work effort. Moreover, the relationships did not disappear when controlling for the three critical psychological states of the job characteristics model (i.e., experienced meaningfulness, experienced responsibility, and knowledge of the results). No cross-lagged relationships were found between enjoyment and work effort. Implications for studies on effort and motivation as well as practical implications are discussed.