People with mental illness are among the most stigmatized and discriminated against as a result of lack of knowledge among the public. Our study explored adolescents' perceptions of people with mental illness through drawings, described these perceptions, and tested the possible changes in perceptions after an educational mental health intervention. Drawings were collected before and after an educational mental health intervention from 59 Greek secondary school students. One group of participants served as the experimental group and received the educational mental health intervention. Content analysis of the drawings was used to analyze data. The drawings provided a clear understanding of adolescents' perceptions towards people with mental illness. After the educational mental health intervention the negative elements presenting the people with mental illness were less among the experimental group, while the drawings among the comparison group did not change. The findings support that educational mental health intervention can have a positive impact on adolescents' perceptions towards people with mental illness. Health professionals can use the findings of our study in order to develop and implement similar interventions.