Objective To construct and develop an intelligent chemotherapy-related symptom management WeChat mini-program for elderly breast cancer patients, and evaluate its usability, so as to provide support for symptom management in elderly breast cancer patients during chemotherapy. Methods Interviews were conducted with 17 elderly breast-cancer patients, 12 family caregivers, and four healthcare professionals to understand the functional requirements of intelligent chemotherapy-related symptom management mini-program for elderly breast cancer patients during chemotherapy, and to determine the functional modules of the mini-program. A multidisciplinary research and development team was set up to build the research and development framework of the WeChat mini-program for elderly breast cancer patients by using the expert meeting method. The mini-program was developed based on the Agile Software Development Principle. The 11 elderly breast cancer patients were selected for usability evaluation based on eye tracking technology. Results The completion rate of representative tasks without errors ranged from 54.55% to 100.00% across six key user scenarios. The System Usability Scale (SUS) score was (74.77±9.52) points. Furthermore, through eye-tracking technology, six specific usability issues were identified. Conclusion The mini program for elderly breast cancer patients has good usability and is suitable for symptom management during chemotherapy for elderly breast cancer patients.