Background Adolescents use social media more frequently than other age groups. Social media has been described as a safe environment for lesbian, gay, bisexual, transgender and queer and/or questioning (LGBTQ) adolescents. As part of mixed-methods research investigating the association between social networks and sexual agency, we present qualitative findings on how LGBTQ adolescents connect online to form support networks. Methods We recruited 30 adolescents aged 14-17years who identified as LGBTQ in terms of their gender or attraction in the longitudinal Social Networks and Agency Project. Semi-structured interviews were conducted online or face-to-face across Australia. Thematic analysis was used to explore perceptions and experiences of participants in relation to social media use and relationships. Results Two overarching themes were identified: LGBTQ adolescents use social media for identity, relationships and wellbeing support. Social media is not always free of discrimination for LGBTQ adolescents. Many LGBTQ participants joined Facebook groups to connect with LGBTQ peers. Facebook was considered a vital support for those with mental health concerns including suicidal ideation. Participants gave and received support from group members, which was considered useful for those feeling isolated or victimised. LGBTQ adolescents formed friendships, romantic relationships and gained information on sex, relationships, and sexual health from these groups. Participants described negative experiences including discrimination within Facebook groups, mismanaged groups and exposure to anti-LGBTQ sentiments. Conclusion Social media is an environment where LGBTQ adolescents can connect, educate and support each other, which may have beneficial effects for this marginalised group. There remain issues with social media including discrimination against and within LGBTQ communities.