Introduction: Breast cancer is ranked first among other cancers in women. Ineffectiveness of current treatments and adverse effects such as multiple organ failure and nephrotoxicity are the common problems faced in cancer therapy. Therefore, alternatives to treat breast cancer metastasis with fewer toxic effects are actively sought-after. Dillenia suffruticosa (DS) commonly known as ‘Simpoh air’ has been a traditional remedy for cancer growth. Therefore, this study investigated the metastasis inhibiting properties of DS root dichloromethane extract (DCMDS) in tumour bearing female BALB/c mice and sub-acute multiple dose oral toxicity upon treatment with this extract. Methods: Forty-eight tumour bearing mice were given either oral treatment of DCMDS (50, 100 and 200 mg/kg) or doxorubicin (2 mg/kg) for 28 days and the degree of metastasis was analysed in each group. Thirty other female BALB/c mice were treated with DCMDS (50, 100 and 200 mg/kg) and the general behaviours, biochemical, haematological and histo- pathological changes were observed. Data were analysed with One-way ANOVA and Dunnet’s test where p