The number of reported cases of bacteremia due to Rothia mucilaginosa (R. mucilaginosa), a component of the normal flora of human gastrointestinal tract mucosa, is limited. We encountered three cases of bacteremia due to R. mucilaginosa during neutropenia after chemotherapy for myeloid malignancies. Although all three patients were successfully treated with antimicrobial agents, one patient developed disseminated lesions in the lungs and soft tissue. The portal of R. mucilaginosa bacteremia is reportedly mucositis or dental disorders; however, no such complications were identified in our patients. Even in the absence of a preexisting portal, R. mucilaginosa should be recognized as a potential causative pathogen of bacteremia during neutropenic periods. Accumulations of cases and isolates are required to further elucidate the risk factors for developing R. mucilaginosa bacteremia, its clinical course, and the optimal antimicrobial treatment.