Background;- Non-communicable diseases are the leading cause for 41 million of the world‘s 57 million deaths.Most Non communicable diseases (Cardiovascular diseases and Diabetes are the highest killing diseases that can mostly occur through the four modifiable risk factors which are physical inactivity, unhealthy diet, harmful alcohol use and tobacco use which are the leading cause for the four metabolic factors (raised BP, raised blood glucose, obesity) which in turn lead to non-communicable diseases.the present study helps to develop programs which help to prevent non-communicable diseases. Objective: -This study assesses knowledge attitude and practice about non communicable diseases and associated factors among high schools students in Addis Ababa. Methodology: - The study has been conducted from November 10-27, 2019 in both selected private and governmental high schools in Addis Ababa and cross sectional study was employed.710 respondents were selected and interviewed from 18 schools from 3 randomly selected sub cities the response rate for the present study was 100%.data was entedred into Epidata version 3.1 and futher multivariate analysis was employed by SPSS version 26. Result: - about61.8% of the study population was females and 38.2 were males. Relating to the age 55.4% of the respondents were lying on the between 15-16 years, which is considered to be the middle adolescents according to the stages of development respectively. This study discovered that only 32.7%, 25.5% and 32.8% of the students have having good knowledge, positive/favorable attitude and practice on non-communicable diseases respectively. Conclusion and Recommendation: - Majority of the students has low knowledge, attitude and practice regarding non-communicable diseases. Thus, immediate actions are suggested with school-based interventions that can improve their knowledge, perception and actions that help them to prevent chronic diseases.