Disclosure of self-injurious thoughts and behaviors (SITBs) is critical to current treatment and prevention programs. Limited research has examined patterns of and barriers to SITB disclosure in adolescents. This work is critical given the limits of confidentiality in this population. Over 1,000 adolescents aged 13–17 with a history of mental health treatment and SITBs were recruited online. Participants reported their history with disclosing SITBs across a range of relationships, honesty in and barriers to disclosure to health care providers, and their experiences with breaches of confidentiality to parents/guardians. We examined relationships among these experiences and a range of outcomes, including perceived likelihood of future disclosure. Participants reported most frequent disclosure of all SITBs to friends, and more frequent disclosure of nonsuicidal self-injury compared to suicide ideation or attempts. Adolescents were most likely to disclose SITBs when directly asked by health care providers, though many participants reported continued SITB concealment. The most commonly endorsed barrier to disclosure was fear that the provider would tell a parent/guardian. Experiences with confidentiality breaches involving a non-collaborative breach were negatively associated with future disclosure, mental health symptoms, and adolescent-parent relationships. SITB disclosure is a cornerstone to their treatment and prevention. Better understanding of to whom and when, barriers, and the impact of disclosure experiences is critical. Our research suggests that most adolescents do not want their parents to know about their SITBs, and that fear of parent involvement prevents disclosure. Results have several implications for SITB assessment across physical and mental healthcare settings.