Introduction: Cardiopulmonary function is compromised in people with Parkinson's Disease (PD) and might be related with mortality in advanced stages of the disease. Therefore, estimating the peak oxygen uptake (VO2peak) to monitor its progression overtime and to prescribe exercise is important in clinical context. This study aimed at developing a VO2peak prediction model for older adults' patients with PD based on functional tests used in the physiotherapy clinical settings. Material and methods: Eighteen patients with PD (63.8 ± 6.6 years old) took part in the study. All participants underwent a basic anthropometry, functional tests, fulfilled a physical activity questionnaire (IPAQ-S) and cardiopulmonary exercise testing on a cycle ergometer. Linear regression and distributional assumptions were performed to develop the prediction model. The Bland-Altman plots were applied for the agreement analysis. Results: The best prediction model included gender, age, waist circumference, BMI, IPAQ-S score, and SPPB functional test score (R2 = 0.87; estimation error: 2.19 ml⋅kg⋅min− 1 ; p < 0.001). The distribution assumptions showed validity of the model (p > 0.05), the estimation bias showed a mean of 0.0056 and no pair of data were outside the limits of agreement according to the Bland-Altman diagram. Conclusions: Accessible, simple, and low-cost variables were useful for validly predicting VO2peak in patients withPD.