ObjectiveThe study aimed to assess diet quality and associated factors among preparatory school students in Awi Zone, Ethiopia.DesignA school-based cross-sectional study design was used in this study.SettingThe study was carried out in Awi Zone, Amhara Region, Ethiopia.ParticipantsA total of 834 preparatory school students participated in the study.Outcome measuresDiet quality was the outcome variable, and it was computed using the dietary diversity score, food variety score and consumption of animal-source foods. Students with high dietary diversity scores, appropriate animal-source food consumption and adequate food variety scores were labelled as having good-quality diets. Data were collected using a pretested structured self-administered questionnaire. Bivariate and multivariable logistic regressions were employed to analyse the data. Variables with p≤0.2 in the bivariate logistic regression analysis were included in the multivariable logistic regression model. Multivariable logistic regression analysis was done to determine the strength of the association. Statistical significance was determined at p value less than 0.05.ResultsOnly 24.7% (95% CI: 21.7%, 27.7%) of preparatory school students had good-quality diets. Being female (adjusted OR (AOR)=2.88, 95% CI: 2.0, 4.1), residing in an urban setting (AOR=1.90, 95% CI: 1.1, 3.2), having an educated mother (AOR=1.78, 95% CI: 1.1, 2.7), having pocket money (AOR=1.83, 95% CI: 1.2, 2.6) and nutrition information (AOR=1.90, 95% CI: 1.2, 3.1), and family monthly income >8000 Ethiopian birrs (AOR=3.90, 95% CI: 2.2, 7.1) were factors significantly associated with having good-quality diet.ConclusionThe majority of the preparatory school students had poor-quality diets. These findings highlight the necessity of nutrition education that considers the sociodemographic characteristics of the students and their families. Implementing income-generating interventions for low-income households was also recommended by the findings.