Back ground: Malnutrition is one of the world’s public health problem and more than half of all infant and child deaths were due to malnutrition directly or indirectly. One of the strategies to promote child health is growth monitoring and promotion services. But, there is limited information on determinants of Growth Monitoring and Promotion service utilization. Objective: To identify determinants of growth monitoring and promotion service utilization among children 0-23 months of age in Legambo district, South Wollo zone, Northern Ethiopia, 2020. Methods: community based un-matched case control study was conducted from March 01-25, 2020 among 363(91 cases and 272 controls) study participants. Samples were selected by using Multi-stage sampling technique. Data were collected by using face to face interviewer administered questionnaire and entered in to Epi data and exported to SPSS version 23 for analysis. Bivariate and multivariable regressions were performed and adjusted odds ratio with its 95% confidence intervals was estimated to identify determinants of growth monitoring and promotion service utilization. Results: Good maternal knowledge (AOR) = 2.42; 95% CI: 1.23, 4.75), mother with favorable attitude (AOR = 2.45, 95% CI; 1.20–4.98), getting nutritional counseling (AOR = 2.34, 95% CI; 1.19–4.56), four and above ANC visits (AOR = 2.46, (95% CI; 1.18–5.16) mothers who have children age 12-17 months(AOR = 3.45, 95% CI; 1.26–9.41) and 18-23 months age (AOR = 4.38, 95% CI; 1.53–12.49), and time to reach the nearest health facility within one hour (AOR = 4.53, (95% CI; 1.99–10.28) were determinants of growth monitoring and promotion service utilization. Conclusion and recommendation: Index child age, good knowledge, favorable attitude, four and above ANC visits, getting nutritional counseling and time to reach the nearest health facility within one hour were determinants of GMP service utilization. Nutritional interventions should give emphasis on nutritional counseling, ANC follow up and accessibility of growth monitoring and promotion. Key Words: Growth monitoring and promotion, less than two years child, Legambo District, Northern Ethiopia.