Background: More than a quarter of children living in Sub-Saharan Africa are underweight. Nutritional deficiency in children increases the risk of infection and affects their mental development. However, there was scarcity of research findings that clearly indicate determinants of academic performance. Therefore, this study was aimed at determining predictors of academic performance with due focus on undernutrition among students attending primary schools., Methods: School based cross sectional study was conducted in February, 2016 among 630 randomly selected students attending primary schools in Hawa Galan woreda. Data were collected through parents/guardians interview, anthropometric measurement of children and school record review. Data were entered into Epidata version 3.1 and analyzed with SPSS Version 20. Anthropometric data were analyzed by WHO Anthro plus software. Pearson's correlation analysis was performed to determine correlation between academic performance and undernutrition. Logistic regression analysis was also performed to assess predictors of academic performance and p < 0.05 was used to declare significant association., Result: Prevalence of stunting, wasting and underweight in this study were 20.6%, 12.7% and 14.3% respectively. This study found a significant correlation between underweight ( r = 0.222, P = 0.040), stunting ( r = 0.214, P = 0.034) and academic performance. Multiple logistic regression analysis also indicated that being female [AOR 1.48; 95% CI (1.16, 3.82)], attending above grade 4 [AOR 2.12; 95% CI (1.98, 4.87)], having educated parents [AOR 2.18; 95% CI (1.43, 4.72)], coming from households with monthly income of more than 2000ETB (~USD91) [AOR 2.85; 95% CI (2.01, 5.21)] and having no parental support during homework [AOR 0.57; 95% CI (0.19, 0.98)] were significantly associated with students' academic performance., Conclusion: Stunting and underweight were found to be correlated with academic performance of students attending primary schools. Nutritional interventions should be considered in the study area. Parents should be encouraged to be involved in their children's schooling., Competing Interests: The authors confirm that there were no competing interests., (© The Author(s). 2017.)