ABSTRACT Background Loneliness, the perception that one’s social relationships do not meet the desire for social connection, is a risk factor for poor mental and physical health. Adolescents with chronic pain experience higher rates of peer loneliness which persists over time. Previous studies used a single loneliness measure, limiting our understanding of the nature of their loneliness. This study describes the types of peer loneliness (intimate, relational, and collective) experienced by these adolescents and the impact that peer loneliness has on pain-related outcomes. Methods A cross-sectional online survey was completed by 128 Canadian adolescents aged 12–18 years who experienced pain for at least 3 months. Validated measures captured demographics, pain-related characteristics, types of peer-related loneliness, measures of social well-being, and mental and physical health outcomes. Results Friedman’s tests of z-scores indicate that participants equally experienced dyadic, relational, and collective peer loneliness. MANCOVA revealed that those who identify as Black were lonelier after controlling for socioeconomic status. Multiple regression showed that loneliness was a robust predicter of worse scores on social well-being and mental health outcomes with males and females equally impacted by loneliness. Despite moderate correlations between loneliness and pain interference and pain intensity, loneliness did not predict school absences, suggesting that loneliness’ influence on physical pain outcomes may be temporally earlier (e.g. contribute to pain chronification). Conclusions Peer loneliness among adolescents with chronic pain negatively impacts their social well-being and mental health outcomes. Interventions addressing loneliness to target all three types of peer loneliness may be key to improving pain-related outcomes.