Medulloblastoma is a metastatic paediatric brain tumour arising in the cerebellum, which also occasionally occurs in adults. It is classified into four major subgroups based on clinical and molecular profiles and current standard of care is to treat patients similarly regardless of classification. Moreover, the clinical interventions of surgery, chemotherapy and radiotherapy come at a price not obvious by the reported survival statistics. Life-long medical problems that result from the collateral damage of healthy tissue by these treatments negatively impact patient quality of life, thus more effective therapeutic approaches for these patients are desperately needed. We used a high-throughput, cell-based assay to identify compounds that target medulloblastoma. Human medulloblastoma cells (n=6) were screened against a library of approximately 3,200 compounds, including US Food and Drug Administration-approved drugs, which identified 50 highly effective compounds. Further in vitro assessment of these compounds identified several chemotherapeutics that enhanced the cytotoxic activity of the clinically-used drug cyclophosphamide (CPA). One of these compounds, a checkpoint kinase inhibitor (CHKi), was further assessed in vivo using mice bearing cortical implants of human medulloblastoma cells engineered to express luciferase. When combined, CPA and CHKi reduced tumour burden as measured by IVIS imaging and significantly increased survival of tumour-bearing animals. Immunohistochemical assessment of vehicle control and drug-treated brain tumours showed the combination treatment significantly decreased the percentage of proliferating (Ki67-postive) cells compared to control tumours (p = 0.007) or tumours treated with CPA alone (p = 0.023), and that CPA and the combination treatment significantly induced apoptosis (measured by cleaved caspase 3 positivity) compared with controls (p = 0.043 and p = 0.007, respectively). These data demonstrate our experimental approach robustly identifies effective new therapies for paediatric medulloblastoma, and our findings strongly suggest that the combination of CPA with CHKi may be a promising new treatment for this disease.