Understanding the distribution of prostate cancer (PC) at various clinical stages of disease is of utmost importance to quantify the cancer care needs of patients and to adequately plan health services. The aim of this analysis is thus to provide a model-based estimation of the number of prevalent PC patients at different clinical stages in the Italian setting. A simulation model of patient transitions was constructed on a yearly basis using data obtained through a literature review on the incidence, prevalence, progression and mortality of PC, with specific focus on disease stage. A total of 462,570 prevalent PC patients were estimated at 1 January 2019. According to the model, 94.8% of them had non-metastatic PC and 5.2% had metastatic disease. Among the non-metastatic patients, most had T1/T2 PC (85.6%), followed by T3/T4 (10.9%) and T0/Tx PC (3.6%). About 20% of the T3/T4 patients had biochemically recurrent PC. Among the metastatic PC patients, 66.1% had castration-resistant PC and 33.9% had hormone-sensitive PC. This study provided original information on the distribution of PC according to different clinical stages that may be useful to define strategies, understand the PC disease pathway, estimate treatment-related needs and, possibly, plan targeted interventions for public health management of prostate cancer in Italy.