The aim of this study was to evaluate the effects of ulinastatin (UTI) and cyclophosphamide (CTX) as mono therapies and as combination therapy on the growth of mouse xenograft breast tumours. MCF-7 breast cancer cells were xenografted into 48 nu/nu nude mice in order to construct a breast cancer xenograft nude mouse model; mice were then untreated (control), or treated with CTX 0.1 g/kg every other day, UTI once a day at 25 000 U (low), 50 000 U (medium) or 100 000 U (high), or CTX + UTI (low), CTX + UTI (medium) or CTX + UTI (high) (n = 6 mice/group). Compared with controls, mice in each drug-treated group had a significantly reduced tumour weight, and protein and mRNA levels of CXC chemokine receptor 4 and matrix metalloproteinase-9 in both the UTI (low, medium and high doses) and CTX groups were significantly reduced, while levels in the UTI (low, medium and high doses) + CTX combination groups were significantly reduced compared with the CTX group and the UTI (low, medium, high) groups. Thus, both UTI and CTX can significantly inhibit xenograft tumours, and the UTI + CTX combination exhibited an additive effect that was superior to both CTX and UTI monotherapy.