Testicular protein kinase 1 (TESK1), a serine/threonine kinase, has been found expressing in various tissues and cell lines. Previous reports have shown that TESK1 plays an important role in regulating actin reorganization of spreading cell on fibronectin via phosphorylating cofilin. Because of the importance of actin reorganization in radial sorting and remyelination of peripheral nerve regeneration, we investigated the spatiotemporal expression of TESK1 in a rat sciatic nerve crush model. We observed that sciatic nerve crush resulted in a significant upregulation of TESK1 from 5 days to 2 weeks and subsequent return to the control level at 4 weeks. At its peak expression, TESK1 expressed mainly in both Schwann cells (SCs) and macrophages of the distal sciatic nerve segment, but had few colocalization in axons. In addition, upregulation of TESK1 was approximately in parallel with Oct-6, and numerous SCs expressing TESK1 were Oct-6 positive. Experiments with Schwann cell primary cultures revealed that TESK1 accumulated at F-actin-rich lamellipodia of the cell periphery when SCs were plated on fibronectin, whereas it was distributed in the cytoplasm in the case of non-stimulated cells. Thus, these findings suggest that TESK1 plays important roles in promyelinating SCs, potentially through subcellular localization change and participation in integrin-mediated actin reorganization.