Protein disulphide isomerase family A3 (PDIA3) has an activity of thioredoxin, widely expressed in multiple tissues and involved in multiple cellular processes. It was recently found in human and mouse sperm cells and could affect sperm–egg fusion. Therefore, the present investigation aims to identify PDIA3 mRNA and protein in rat testis and sperm cells. Rat PDIA3 cDNA was cloned by RT-PCR. The cRNA riboprobe was transcribed from PDIA3 cDNA and was used to display PDIA3 mRNA location in rat testes by in situ hybridization. PDIA3 protein distribution was also observed in testis and sperm cells by immunohistochemistry and immunocytochemistry, respectively. The rat PDIA3 transcript and protein were localized in the cells from spermatocytes to the spermatozoa phases of rat testes, mostly in the pachytene spermatocytes. PDIA3 protein was also observed on the intact sperm membrane including the tail. The rat PDIA3 gene is transcribed and translated through the whole spermatogenesis process, and the PDIA3 protein is spread all over the sperm cell membrane. The results provide some primary information about PDIA3 in testis and sperm for further study on PDIA3 function in rat spermatogenesis and sperm–egg fusion.