Khat use among high school students has become an increasing public health concern on account of the implications of early substance dependence on the future of the youth. Many studies have been done on the prevalence of khat chewing and factors associated with it but little is done on the bio psychosocial effects of khat use. This study explored the bio psychosocial effects of khat use on high school students in Lideta Sub-city, Woreda 01(A.A). The study applied the qualitative method with exploratory purpose. The qualitative method adopted a case study approach. In-depth interview, key informant interview, focus group discussion and observation were used to collect data and thematic analysis was applied to analyze data. It employed the non-probability sampling method with both purposive and snowball sampling techniques. Thernfindings of the study showed that khat use has adverse health effects on the users (high school students in this study) which include biological, psychological and social effects. Accordingly, the major biological effects of khat use include gastrointestinal effects, effects on the reproductive system, cardiovascular effects and other physiological problems associated with ‘mirqanna’ and withdrawals. The psychological effects of khat use include psychological dependence, major psychiatric disorders (such as anxiety, insomnia, nightmare, depression, euphoria and excitement) and other psychological problems associated with ‘mirqanna’ andrnwithdrawals. Socially, khat use is associated with criminal and anti-social activities, interactionrnproblems, wastage of time, low academic performance or low productivity, family discord andrnbreakdown, and social stigma and discrimination. Moreover, the study revealed that khat usernamong high school students has an impact on the general well-being of the individual users andrnthe society. Finally, coordinating with different stakeholders, the establishment of a departmentrnor commission (which should be assigned with different responsibilities) at the national levelrnunder the supervision of Ministry of Health, Ministry of Education or Ministry of Women,rnChildren and Youth Affairs is highly recommended. Besides, incorporating character count traitsrnprograms in the education policy; filling the legal gap with regard to khat use; and expandingrnrehabilitation centers for the students affected by khat use are also recommended.rnKey words: Exploring, Bio psychosocial effects, Khat use, High school students, Addis Ababa