Introduction: Abuse of substances creates a great threat to the health, social and economic condition of individual, family, community and to the nation. In the past two decades’ abuse of substances is an important public health concern among people, especially among adolescents. Objective: The major aims of the study were to assess the level of knowledge about effects of substance abuse among adolescents. Methods: This was a cross-sectional descriptive study carried out among 70 adolescents. Data analysis was done using SPSS version 25. Results: The socio-demographic characteristics of the adolescents were as fallows. 57.14% of respondents’ age was 16-17 years, approximately 82% of respondents belonged to Muslim religion. The majority believed that substance use would lead to unsatisfactory health such as respiratory problems 61.4%, 82.8% think that depression is the main mental effects and 61.42% said that, lack of parent understanding is the main social effect.62% Percentage distribution of knowledge of adolescents, 37.14% participants had poor knowledge, 55.71% respondents had average knowledge and only 37.14% had good knowledge regarding effects of substance abuse. Conclusion: After thorough analysis of the data, concluded that adolescents’ knowledge regarding effects of substance abuse should be increased in order to promote their health and there by avoid the consequences occurring due to substance abuse.