Assessment of treatment response in patients (pts) with leptomeningeal metastases (LM) represents a significant challenge and standardized criteria are needed. In 2017, the RANO LM Working Group proposed a standardized scorecard to evaluate MRI findings (further simplified in 2019). Here, we aim to validate the prognostic impact of response to treatment assessed using this tool in a multicentric cohort of breast cancer (BC) pts. Pts with BC‐related LM diagnosed at two institutions between 2005 and 2018 were identified. Baseline and follow‐up MRI scans were centrally reviewed and response assessment was evaluated using 2019 revised RANO LM criteria. A total of 142 pts with BC‐related LM and available baseline brain MRI imaging were identified; 60 of them had at least one follow‐up MRI. In this subgroup, median overall survival (OS) was 15.2 months (95%CI 9.5‐21.0). At first re‐evaluation, radiological response by RANO criteria was: complete response (CR) in 2 pts (3%), partial response (PR) in 12 (20%), stable disease (SD) in 33 (55%) and progression of disease (PD) in 13 (22%). Median OS was 31.1 months (HR 0.10, 95%CI 0.01‐0.78) in pts with CR, 16.1 months (HR 0.41, 95%CI 0.17‐0.97) in pts with PR, 17.9 months (HR 0.45, 95%CI 0.22‐0.91) in pts with SD and 9.5 months in pts with PD ( P = .029). A second blinded evaluation showed a moderate interobserver agreement ( K = 0.562). Radiological response according to 2019 RANO criteria is significantly associated with OS in pts with BC‐related LM, thus supporting the use of this evaluation tool both in trials and clinical practice.