It is generally believed that cell-to-cell cross-talk and signal transduction are mediated by cell surface molecules that play diverse and important regulatory roles in spermatogenesis and fertilization. Recently, we identified a novel plasma membrane-associated protein, TES101-reactive protein (TES101RP, or TEX101), on mouse testicular germ cells. In this study, we investigate Tex101 mRNA expression in the adult mouse testis using in situ hybridization, and we examine the fate of TEX101 during sperm transport by immunohistochemical and Western blot analyses. Tex101 mRNA was expressed in a stage-specific manner in spermatocytes and in step 1–9 spermatids of the testis, but not in spermatogonia. Although the TEX101 protein remained on the cell surfaces of step 10–16 spermatids and testicular sperm, it was shed from epididymal sperm located in the caput epididymidis. The results of this study provide additional information on germ cell-specific TEX101 expression during spermatogenesis and post-testicular sperm maturation.