Objective: There is a lack of evidence concerning undernutrition (underweight and stunting) among adolescent girls in the study area, therefore, this study aimed to assess the magnitude of undernutrition and associated factors among adolescent girls in Hawzen woreda, Northern Ethiopia.Results: This study found that 32.2% and 33.2% of school adolescent girls were underweight and stunted respectively. Illiterate fathers were higher among underweight adolescent girls as compared to those normal-weight adolescent girls (AOR = 1.4, 95% CI; 1.1, 1.7). Underweight adolescents were higher among low-grade level adolescents (grade 4-8) as compared to grade 9-12 adolescents (AOR = 2, 95% CI; 1.4, 2.6). Unemployed mothers were higher among stunted adolescent girls as compared to the counterpart (AOR = 2.2, 95% CI; 1.1, 3.3). It would be good to consider the above-mentioned factors during the nutritional intervention of adolescents.