BackgroundSaccharomyces cerevisiaeis ubiquitous in the gastrointestinal tract and known as brewer's or baker's yeast. We experienced a case ofS. cerevisiaeandCandida glabrataco-infectious bloodstream infection.It is rare to detect bothS. cerevisiaeandCandidaspecies in blood cultures together.CaseWe treated a 73-year-old man who developed a pancreaticoduodenal fistula infection after pancreaticoduodenectomy. The patient had a fever on postoperative day 59. We took blood cultures and detectedC. glabrata. Thus, we started micafungin. On postoperative day 62, we retested blood cultures, and detectedS cerevisiaeandC. glabrata. We changed micafungin to liposomal amphotericin B. Blood cultures became negative on postoperative day 68. We changed liposomal amphotericin B to fosfluconazole and micafungin because of hypokalemia. He got well, and we terminated antifungal drugs 18 days after the blood cultures became negative.ConclusionCo-infection withS. cerevisiaeandCandidaspecies is rare. In addition, in this case,S. cerevisiaedeveloped from blood cultures during micafungin administration. Thus, micafungin may not be effective enough to treatS. cerevisiaefungemia, although echinocandin is considered one of the alternative therapy forSaccharomycesinfections.