Introduction: In Developing Countries including Ethiopia, mental health is not only a public concern; but also a developmental issue. Depression and anxiety are the commonest mental health disorders and often somatic symptoms co-exist with them. Adolescents with common mental health problems are associated with increased risk of suicide, future unemployment, and poor quality of life. Little is known about the mental health of adolescents in the Ethiopia. Thus, this study aimed to assess the magnitude and determinants of depression, anxiety, and somatic symptoms among high school and preparatory school adolescents in Gondar town. Methods  Institution based cross-sectional study was conducted from June 8 to 24, 2022. Two-stage stratified random sampling was used to select 1407 high school and preparatory school adolescents in Gondar town. Data were collected through structured and standard self-administered questionnaires.  STATA version 16 and AMOS version 21 were used for analysis. Non-recursive structural equation modeling was employed to assess the direct, indirect, and total effects of the predictors. Degree of relationship was interpreted based on adjusted regression coefficients with corresponding 95% confidence interval. Results  Magnitude of anxiety, depression, and somatic symptoms were 25.05% (95%CI: 22.8, 27.5), 28.21 (95% CI: 25.8, 31%), and 25.24(95% CI: 23, 27.6%), respectively. High self-rated academic ability (β=-0.03, 95% CI: -0.065, -0.006) and high perceived social support (β=-0.22, 95% CI: 0-.304, -0.139) had significant negative effect on anxiety. High levels of depression had a direct positive effect (β= 0.74, 95% CI: 0.508, 1.010) on anxiety. High level of stress had significant direct (β=0.54, 95% CI: 0.293, 0.745) and indirect (β=0.57, 95% CI: 0.379, 0.814) positive effect on anxiety. High level of anxiety was significantly related with high level of depression (β=0.74, 95% CI= 0.483, 1.081). High perceived social support (β= -0.13, 95% CI: -0.229,-0.029), and having a history of death of beloved one within the past six months (β= 0.03, 95% CI: 0.014, 0.256) had a significant direct positive effect on depression. Having medically confirmed chronic illness (β=0.21, 95% CI=:0.114, 0.311), being female (β= 0.06, 95% CI= 0.003, 0.109) and high level of stress (β= -0.06, 95% CI: -0,454, 0.247) had significant indirect effect on depression. Stress (β= 0.86, 95% CI: 0.700, 1.025), anxiety (β=0.66, 95% CI: 0.270, 3.825) and depression (β= 0.96, 95% CI: 0.167, 3.629) were significant predictors of somatic symptoms. Conclusions and recommendations  Magnitude of anxiety, depression, and somatic symptoms were moderate. Self-rated academic ability, physical trauma, school type, sex, stress, ever use of alcohol, perceived social support, death of beloved one, and having medically confirmed chronic illness were independent predictors of anxiety, depression and somatic symptoms. The bidirectional relationship between anxiety and depression was significant. Emphasis should be given to the prevention and management of mental health in the adolescent, particularly targeting adolescents with the aforementioned factors.