Thermoascus crustaceus is a thermophilic fungus and the teleomorph form of Paecilomyces crustaceus. Thermoascus spp. have been rarely isolated from human mycoses as etiological fungal agents. We believe that our patient is the first case of catheter colonization with Thermoascus crustaceus. In a 50-year-old male patient undergoing chronic peritoneal dialysis, the mold was isolated from three separate, consecutive dialysate fluid specimens and peritoneal catheter tip. The patient had slight clinical findings and he was treated by early catheter removal without antifungal treatment. Therefore this case was considered as the colonization of the peritoneal catheter rather than peritonitis. Consequently, we think that the human pathogen fungal spectrum will continue to enlarge.