How can nurses assess the self‐management of lower urinary tract symptoms (LUTS) in patients with cancer after radical prostatectomy (RP)? Patients with prostate cancer who have undergone RP experience multiple LUTS. This study aimed to develop a self‐management scale for LUTS in patients with cancer following RP (SMS‐LUTS‐RP), as well as to verify its reliability and validity. LUTS has physical, social, and psychological consequences for patients. As a result, patients are forced to self‐manage their LUTS and LUTS‐related issues. However, no indicators exist to assess self‐management of LUTS. A total of 246 individuals were surveyed. A 49‐item scale draft, whose content validity and face validity were confirmed, was used to develop a questionnaire for patients with LUTS after RP. The reliability and validity were determined using by item analysis, exploratory factor analysis, confirmatory factor analysis, and Cronbach's α coefficient. The exploratory factor analysis produced the following 18 items on five extracted factors: ‘monitoring of urinary status,’ ‘coping with daily life difficulties due to LUTS,’ ‘collaboration with medical professionals,’ ‘continued training to improve LUTS,’ and ‘living with LUTS.’ The goodness‐of‐fit‐index (GFI) for confirmatory factor analysis was 0.876, and the root mean square error of approximation was 0.075. Cronbach's α coefficient was 0.754–0.820. SMS‐LUTS‐RP has desirable psychometric properties and can assess the cognitive and behavioural aspects of self‐management of LUTS in patients with cancer who have undergone a RP. This scale can be used to provide individualized self‐management support according to living conditions.