Objectives This study aimed to evaluate the effectiveness of family-based nursing interventions in improving mothers’ knowledge, attitudes, and self-efficacy to prevent stunting among children under 2 years of age in Indonesia. Methods A quasi-experimental study was conducted from June to December 2024 in Alor District, East Nusa Tenggara, Indonesia. Sixty mothers of children aged 0–24 months were recruited using convenience sampling and assigned to either an intervention group ( n = 30) or a control group ( n = 30). The intervention group received seven structured sessions of a family-based nursing intervention grounded in Family-Centered Care and Social Cognitive Theory. In contrast, the control group received routine health education from local community health centers. Knowledge, attitudes, and self-efficacy were measured using validated questionnaires at baseline, post-intervention, and a three-month follow-up. Data were analyzed using independent-sample t -tests and a mixed repeated-measures analysis of variance. Results All 60 participants completed the study. Independent-sample t -tests revealed no significant differences between the two groups at baseline for knowledge ( t = −0.682, P = 0.498), attitudes ( t = 0.655, P = 0.515), and self-efficacy ( t = 1.671, P = 0.100). A mixed repeated-measures analysis of variance demonstrated significant group, time, and group × time effects on knowledge, attitudes, and self-efficacy (all P < 0.001). Pairwise comparison revealed that the scores at post-intervention and three-month follow-up were significantly higher in the intervention group for all three variables (all P < 0.001). Conclusions The family-based nursing intervention effectively enhanced maternal knowledge, attitudes, and self-efficacy regarding stunting prevention. These findings underscore the importance of incorporating structured, family-centered interventions into community-based public health programs to reduce the risk of stunting. © 2026 The Authors.