Stunting is a chronic nutritional problem that may originate during pregnancy and impair child growth and development. The impact of self-help group–based nutrition education on pregnant women’s knowledge, attitudes, and practices related to stunting prevention remains unclear. This study aimed to evaluate the effectiveness of a self-help group intervention in improving pregnant women’s knowledge, attitudes, and practices regarding balanced nutrition for preventing stunting. Methods: This quasi-experimental pretest–posttest control-group study was conducted in Ingin Jaya District, Aceh Besar, from June to July 2024. Sixty pregnant women were divided into intervention and control groups, with 30 participants in each group. The intervention comprised six participatory self-help group sessions delivered over six weeks duration. Knowledge, attitudes, and practices were assessed using a structured questionnaire containing 21 knowledge items, 12 attitude items, and 18 practice items. Data were analyzed using Wilcoxon’s test. Results: The intervention was associated with significant improvements in knowledge (p<0.001) and practice (p<0.001). No significant improvement was observed in attitude scores (p=0.705). In conclusion, the self-help group intervention improved pregnant women’s knowledge and practices related to balanced nutrition for stunting prevention, but did not improve their attitudes. This approach may support maternal nutritional education in community settings.