BACKGROUND: Falls in older adults with cancer are common, yet factors associated with fall-risk are not well-defined and may differ from the general geriatric population. This study aims to develop and validate a model of factors associated with prior falls among older adults with cancer. METHODS: In this cross-sectional secondary analysis, two cohorts of patients aged ≥ 65 with cancer were examined to develop and validate a model of factors associated with falls in the prior 6 months. Potential independent variables, including demographic and laboratory data and a geriatric assessment (encompassing comorbidities, functional status, physical performance, medications, and psychosocial status), were identified. A multivariate model was developed in the derivation cohort using an exhaustive modeling approach. The model selected for validation offered a low Akaike Information Criteria value and included dichotomized variables for ease of clinical use. This model was then applied in the validation cohort. RESULTS: The development cohort (N = 498) had a mean age of 73 (range 65-91). Nearly one-fifth (18.2%) reported a fall in the prior 6 months. The selected model comprised nine variables involving functional status, objective physical performance, depression, medications, and renal function. The AUC of the model was 0.72 (95% confidence intervals 0.65-0.78). In the validation cohort (N = 250), the prevalence of prior falls was 23.6%. The AUC of the model in the validation cohort was 0.62 (95% confidence intervals 0.51-0.71). CONCLUSION: In this study, we developed and validated a model of factors associated with prior falls in older adults with cancer. Future study is needed to examine the utility of such a model in prospectively predicting incident falls.