Breast cancer is the most common malignancy in women. Apoptosis is important for tumor suppression and may delay cancer progression. It was found that shikonin induced apoptosis in 4T1 murine mammary cancer cells and MDA‑MB‑231 human breast cancer cells in vitro. Total p38 and c‑Jun N‑terminal kinase (JNK) levels were maintained in 4T1 cells, and p38 phosphorylation, but not JNK phosphorylation, was significantly increased. Caspase‑3/7 activity was detected, which suggested that the p38 pathway, but not the JNK signaling pathway, induced apoptosis in 4T1 cells. The anti‑tumor effects of shikonin on orthotopic mouse models were also examined. On day 7 after inoculation of 4T1 cells into mice, tumor volumes in the shikonin‑treated and the control groups began to differ. On day 13, tumors were weighed, and shikonin was revealed to suppress tumor growth in the orthotopic 4T1 model in vivo. In conclusion, shikonin is a potential anti‑tumor drug for breast cancer.