EW02, a polysaccharide-enriched crude extract from black soybean, has been shown to assist hematopoiesis in chemotherapy‑treated animals. The present study aimed to clarify the safety, quality of life (QOL) and efficacy for myelopoiesis of EW02 administration in early breast cancer (EBC) patients receiving adjuvant chemotherapy. A total of 60 eligible EBC patients were enrolled in a randomized, double‑blinded trial, 40 of whom were prescribed 700 mg oral EW02 three times daily for 15 days in chemotherapy cycle (C)2. The remainder were prescribed a placebo. All subjects took EW02 in C3 for 15 days. Blood samples were collected at different time‑points for determining the blood cell count, and the serum level of granulocyte colony‑stimulating factor (G‑CSF) and interleukin (IL)‑6. All patients tolerated EW02 well without severe side‑effects. QOL evaluation showed that only the score of one questionnaire section (QLQ‑C30) was significantly increased at C1 day (D)8 to C2D8 when the EW02 and placebo groups were compared (P=0.045). No significant myelopoiesis recovery, and no incremental change in IL‑6 and G‑CSF levels were found in C2. Subgroup analysis showed a slightly lower decrease in absolute neutrophil count (ANC) in the EW02 patients who underwent Adriamycin + cyclophosphamide treatment compared with the placebo group. Although EW02 failed to show efficacy for myelopoiesis in the present study, EW02 was still well tolerated in EBC patients who underwent adjuvant chemotherapy.