Background: Previous research suggests attachment is a vulnerability factor for self-harm thoughts and behaviors in adults. Yet, few studies have investigated this relationship during adolescence, although adolescence is a critical period for changes in attachment relationships and self-harm onset. Whether and how attachment relates to self-harm thoughts and behaviors as measured in daily life is also unknown. Aims: To investigate whether and how paternal, maternal, and peer attachment are associated with lifetime and current adolescent self-harm thoughts and behaviors. Additionally, to examine how different attachment bonds interact in relation to lifetime and current adolescent self-harm thoughts and behaviors. Method: Pre-existing data from N = 1,913 adolescents of the SIGMA study were used. Attachment and lifetime history of self-harm thoughts and behaviors were measured via retrospective questionnaires. Current self-harm thoughts and behaviors were assessed 10 times per day for 6 days using the experience sampling method (ESM). Results: Paternal and maternal attachments were associated with lifetime self-harm thoughts and behaviors and current self-harm thoughts. No significant associations were found between peer attachment and self-harm outcomes. Limitations: Some analyses were underpowered. Conclusion: Our results highlight the importance of parent–child attachment relationships, which may be intervention targets for prevention and treatment of adolescent self-harm.