Introduction: Rising use of electronic nicotine delivery system (ENDS) among young people, especially those who have never smoked, has received considerable attention from the health community. However, fewer studies have examined the mental health impacts of ENDS use. We addressed this gap by exploring the stigma, altered self-perceptions and negative affect experienced by adolescents who assessed themselves as addicted to using ENDS. Methods: We interviewed 20 adolescents aged 16–18 who lived in Aotearoa New Zealand and assessed themselves as moderately or highly addicted to ENDS use. Using in-depth, semistructured qualitative interviews, we explored participants’ experiences of addiction and its effects on their well-being. We interpreted the data using an inductive reflexive thematic analysis approach. Results: We identified four key themes. First, addiction to ENDS use adversely affected participants’ physical and mental health. Second, addiction greatly diminished the pleasurable effects ENDS use first provided and participants who initially enjoyed using ENDS now felt unable to stop. Third, participants felt judged, stigmatised and belittled by others who did not understand their struggle with addiction. Fourth, they experienced several negative emotions, including self-blame, regret, disappointment and embarrassment that diminished how they saw themselves. Conclusions: We extend earlier studies by probing the mental health burden ENDS use imposes on young people, offer new insights into how they experience addiction and outline potential policy responses. Measures reducing young people’s access to ENDS are urgently needed alongside empathetic, youth-oriented cessation support.