One of the most common nutritional problems in Indonesia is undernutrition among toddlers. According to WHO, approximately 17% or 98 million toddlers in developing countries experience undernutrition. Undernutrition is influenced by socioeconomic factors, dietary patterns, and exclusive breastfeeding. This study aims to analyze the relationship between socioeconomic factors, dietary patterns, and exclusive breastfeeding with undernutrition in toddlers in Merak Village. This study was a case-control design with a sample size of 50 for each group, calculated using the Lemeshow formula and selected through purposive sampling. The dependent variable of this study is undernutrition, which was measured using weight-for-age (W/A). Data analysis was analyzed by chi-square tests and multivariate analysis throught logistic regression. The research instruments included questionnaires. The bivariate test results obtained significant relationships between undernutrition and several factors were family income (p-value 0.012; OR 0.316), meal frequency (p-value 0.000; OR 11.156), food intake amount (p-value 0.000; OR 24.571), and exclusive breastfeeding (p-value 0.000; OR 0.141). Meanwhile, no significant relationships were found for maternal education (p-value 0.288; OR 0.566), father's occupation (p-value 0.691; OR 1.000), and mother's occupation (p-value 0.161; OR 1.909). The multivariate test results indicated that meal frequency, food intake amount, and exclusive breastfeeding are factors influencing undernutrition in toddlers. The most dominant factor is exclusive breastfeeding. Conclusion family income, dietary patterns, and exclusive breastfeeding are risk factors for undernutrition in toddlers.