Toddler nutrition monitoring at Puskesmas Kotabumi II is still largely paper-based, making data recording, growth assessment, and reporting time-consuming and prone to errors. This study develops and evaluates an Android-based Toddler Nutrition Monitoring System using Kotlin, Firebase Authentication, and Cloud Firestore following the Research and Development prototype approach. The system automates weight-for-age (W/A) z-score classification based on the World Health Organization (WHO) Child Growth Standards and the Indonesian Ministry of Health Regulation No. 2 of 2020. It also provides toddler data management, growth-record entry, growth-chart visualization, weighing reminders, role-based access (nutrition officers, health center managers, and parents), and CSV/PDF report export. Functional evaluation using Black Box Testing across 15 test scenarios showed that all system functions operated as expected. User Acceptance Testing (UAT) involving 20 respondents from nutrition officers, Posyandu cadres, and parents achieved an average satisfaction score of 88.3%, indicating a very good level of usability and user acceptance. Although the current prototype supports only the W/A index and has not yet been validated against an independent anthropometric reference such as WHO Anthro, the results demonstrate that the proposed system is a feasible and well-accepted solution for improving the efficiency and quality of toddler nutrition monitoring in primary healthcare settings.