Background: Several studies indicate that prevalence rates of the individual symptoms: depression, anxiety and stress are growing among adolescents. Objective: to evaluate the extent of depression, anxiety, and stress among secondary school students in Baghdad, Iraq. Method: A school based cross-sectional study was conducted during the school year 2007/2008, from October 2007 to March 2008. The sample included secondary school students in Baghdad, Iraq. Cluster sampling method was used. The students were evaluated by well-trained group of teachers. Data were collected using the Arabic version of the Depression Anxiety Stress Scale (DASS-42) while sociodemographic and environmental data, as well as the presence of associated psychological factors, were collected via a questionnaire devised for the study. Formal consent from students was taken. Statistical analysis was conducted using the Statistical Package for the Social Sciences (SPSS, Version 15 for Windows). Results: A total of 48720 secondary school students participated in the study; 62.5% had symptoms of at least one of the three studied symptoms. Depression, anxiety, and stress symptoms were 29.4 %, 40.6% and 51.1% respectively. Statistical analysis showed highly significant findings (P<0.001). Conclusion: High prevalence rates of depression, anxiety and stress symptoms among Iraqi secondary school students indicated exposure to sever ongoing stresses. Psychosocial support and stress resilience reduced the severity of these symptoms.