Background: Mental health in adolescents are very important. Many of them preparing for university admissions and with the COVID-19 they are at higher risk of developing mental health problems Purpose: The objective of this study was to assess depression, anxiety, and stress among high school students during the COVID-19 pandemic and to study the associated factors for depression, anxiety, and stress. Methods: Cross sectional online survey, high school students from grades 10-12 who could access the internet were invited to participate in completing the online questionnaire. A total of 732 students participated. Sociodemographic factors were analyzed by descriptive statistics and the DASS-21 scale was used to assess the levels of Depression, Anxiety, and Stress.  Result: The majority of students displayed normal levels of depression, anxiety, and stress at (n=486, 66.39%), (n=479, 65.44%) and (n=682, 93.17%) respectively. The associated factors for depression was gender while the associated factors for stress was class level.  Conclusion: The outbreak of the COVID-19 affected the mental health of many high school students. During the lockdown period students had to adjust their lifestyle including learning style therefore leading to some mental health affected. The associated factors for depression was gender while the associated factors for stress was class level. Therefore understanding students mental health associated factors and giving appropriate support could help prevent mental health problems.