Young people’s perspectives about mental health concepts shape both their interactions with sufferers of mental illness and their actions related to their own mental health. The current study employed a cross-sectional qualitative design to explore how adolescents (aged 12–18 years) speak about mental health and illness in order to gain insight into young people’s perceptions and experiences and contribute to shaping approaches to policy and practice. When discussing mental health concepts and appropriate behaviours toward sufferers of mental illness, adolescents conveyed a sense of acceptance and understanding of the potential complexity and severity of mental health problems. In contrast, when discussing mental health in the context of their own lives, a stronger sense of scepticism was conveyed, with students expressing difficulty with the lack of visible markers of mental health and confusion determining authenticity in the mental health states conveyed by their peers. Interestingly, adolescents interviewed commonly conveyed the notion that young people may exaggerate or “fake” a mental illness for personal gain. Adolescent perceptions of mental health and illness hold practical implications for policy and school-based programs aimed at improving mental health knowledge, attitudes and behaviours among youth.