Breast cancer affects one in every eight women, and has been associated with higher rates of female mortality than any other cancer type, with the exception of lung cancer. It has been reported that chondromodulin I (ChM-I) was able to suppress tumor angiogenesis and growth in vivo. In order to investigate the antitumor action of ChM‑I on human breast cancer cells, a plasmid expressing ChM‑I was constructed and transfected into human breast cancer cells using an adenoviral vector. Reverse transcription‑polymerase chain reaction detected ChM‑I expression in human breast cancer cell lines, whereas no expression was detected in the control groups. In order to assess the effect of ChM‑I on human breast cancer cells, cell counting kit‑8 (CCK‑8) and colony formation analyses were used to detect tumor cell proliferation, and the proliferation of ChM‑I‑transfected cells was significantly reduced, as compared with the control. In addition, the mRNA expression levels of cell cycle‑associated genes in ChM‑I‑transfected cells were significantly decreased, as compared with the control, which suggested that ChM‑I transfection was able to inhibit the expression of genes associated with the cell cycle. The results of the present study indicated that ChM‑I was able to inhibit the growth of breast cancer cells; thus suggesting that ChM-I may have potential clinical applications in the treatment of breast cancer.