Background: Complementary feeding monitoring is essential to ensure children receive appropriate nutrition. Objective: To develop a digital complementary feeding monitoring application and to evaluate its effect on mothers and their children. Methods: The study was conducted in two phases among mothers with children aged 6 to 12 months in Indonesia. In the first phase, a complementary feeding-monitoring system application was created. In the second phase, the impact of the application on maternal knowledge and feeding practices as well as children’s nutritional status was examined using a two-arm experimental design (intervention and control). The intervention was conducted for 3 months. Both groups received the same educational content, through the application (intervention) or a WhatsApp group (control). Results: A total 100 mothers were included; 42 in the intervention group and 58 in the control group. The intervention group showed a significant increase in knowledge (P<0.001), attitude (P<0.001), and practices (P=0.003) compared to the control group. The intervention group showed also a significant increase in nutrient intake, including energy (P=0.008) and protein (P<0.001) but not fat (P=0.058). The length-for-age z-score indicator showed a significant reduction in growth faltering in the intervention group (-0.14 ± 0.59) compared to the control group (-0.70 ± 0.84, P<0.001). Although weight-for-age z-score increased in the intervention group, the increase was not significantly different between groups (P=0.759). Conclusions: A digital complementary feeding monitoring application is beneficial for improving complementary feeding practices, enhancing nutrition intake, and potentially in preventing stunting in children aged 6 to 12 months. © 2026, Egyptian Community Medicine Association. All rights reserved.