BACKGROUND Underweight, wasting, and stunting are the commonest nutritional disorders among children, especially in developing countries. The aim of this study was to assess the prevalence and determinant factors of underweight, wasting, and stunting among school-age children in 2019. METHODS A cross-sectional study was conducted in the five special districts of South Gondar Zone, among 314 school-age children. WHO AnthroPlus software was used to build Z-scores from anthropometric measurement. The data were analyzed by SPSS Version 20. The degrees of association were assessed using adjusted odds ratio (AOR) and 95% confidence interval during multivariable logistic regression. A P-value less than 0.05 was considered to be statistically significant. RESULTS Of the total study participants, 232 (77.3%) were from public schools. The mean±standard deviation (SD) of height of children was 132.9±9.8 cm, and the mean±SD weight of children was 27.7±5.8 kg. The prevalence of stunting, wasting, and underweight was 11%, 6.3%, and 11.4%, respectively. Students who ate their breakfast rarely were 8-times more likely to be underweight than those who ate their breakfast always (AOR=7.9, 95% CI=4.8-14.8). Those who were sick in the past 2 weeks were more likely to be underweight than their counterparts (AOR=7.3, 95% CI=2.8-14.4). Those who never consume milk or milk products were 6.5 (AOR=6.5, 95% CI=1.7-23) times more likely to be stunted than those who consumed this always. Sickness in the past 2 weeks prior to data collection was significantly associated with thinness (AOR=6 0.9, 95% CI=4.1-10.1). CONCLUSIONS The overall prevalence of wasting, stunting, and underweight was a mild public health problem in the study area.