Voluntary HIV counseling and testing (VHCT) is one of the key strategies in the prevention of HIV in Ethiopia. However, utilization of the service among adolescents has been reported as low by previous studies. The purpose of this study was to investigate adolescents' knowledge and attitudes towards VHCT services among adolescents attending high school in Addis Ababa, Ethiopia. A cross-sectional school-based design using quantitative methods was employed to attain the objectives of the study. Data collection was done using self-administered structured questionnaires among 378 adolescent high school students. Data was analyzed using the Statistical Package for Social Sciences (SPSS). The findings revealed that 75.7% of students are aware of the VHCT services; 62.2% use the services and suggested that VHCT services should be located in schools and youth clubs for better access by adolescents. Thirty-two percent of respondents rated themselves at risk of HIV infection and 35.2% werenot willing to disclose their HIV positive status to anybody. The findings of the study clearly indicate a need for a more accessible voluntary HIV counseling and testing services for adolescents.