IT consumerization – defined as the use of privately-owned IT resources for business purposes – is steadily growing, thus creating new challenges for enterprises. While numerous practitioner studies suggest a positive effect of this trend on employee work performance, IS research still lacks a systematic understanding of the forces underlying this relationship. In order to close this research gap, we derive three major effects of IT consumerization on employees: 1) an increased workload 2) an elevated autonomy and 3) a higher level of competence. Drawing on cognitive stress model and self-determination theory, we develop an innovative theoretical model of the relationships between IT consumerization and work performance. We then conduct an embedded single-case study, in order to evaluate the constructs and relationships of our structural model by means of qualitative research. Subsequently, the implications for theorizing and practicing IT consumerization are discussed and suggestions on further developing this study are presented.