IMPORTANCE: Characterizing cannabis use (CU) rates in pediatric pain is critical as adolescence is a period of increased substance use and risk for negative outcomes. Youths with chronic pain may engage in CU to cope with symptoms. OBJECTIVE: To examine CU rates, risk perceptions, and motivations for use among treatment-seeking youths with diagnosed pain disorders. DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional survey study conducted from September 2021 to May 2024 at a pain treatment clinic at a pediatric hospital in the Northeast United States. Participants were 251 adolescents receiving treatment for diagnosed pain conditions. Of 312 approached, 40 did not complete the survey; 17 were excluded. EXPOSURES: Validated self-report measures assessing demographics, pain, and substance use. MAIN OUTCOMES AND MEASURES: CU rates, motivations for use, and perceived risks. RESULTS: Of 245 adolescents providing complete data (mean [SD] age 16.9 [1.4] years; 168 [68.6%] female; 1 [0.4%] American Indian, 3 [1.2%] Asian, 3 [1.2%] Black, 19 [7.8%] Hispanic or Latino, and 201 [82.1%] White), 62 (25.3%) endorsed lifetime CU, with a mean (SD) age at first use of 15.3 (1.9) years. Among those endorsing CU, past-year prevalence was 90.2% (56 of 62 participants) and past-month prevalence was 64.5% (40 of 62 participants). The CU group was older (mean difference, 0.9 years; 95% CI, 0.5 to 1.2 years; P < .001), included fewer female participants (difference, -14.0%; 95% CI, -32.6% to -2.9%; P = .03), and reported greater pain interference scores (mean difference, 2.7; 95% CI, 0.8-4.6; P = .01) and depressive symptoms scores (mean difference, 6.2; 95% CI, 2.8-9.5; P < .001) compared with the no CU group. The no CU group perceived cannabis as riskier (odds ratio, 2.37; 95% CI, 1.28-4.39; P = .01). Among youths endorsing CU, 48 of 62 (77.4%) endorsed instrumental use (IU) to alleviate psychological or physical symptoms (primarily pain, sleep, and anxiety), representing an overall IU prevalence of 19.6% (48 of 245 participants). Youths reporting IU were younger (mean difference, -0.7 years; 95% CI, -1.3 to -0.1 years; P = .04) and reported greater functional disability scores (mean difference, -8.4; 95% CI, 2.1 to 12.6; P = .01) compared with the no IU group. CONCLUSIONS AND RELEVANCE: In this cross-sectional study, approximately 25% of treatment-seeking youths with chronic pain reported CU, with more than 75% using cannabis instrumentally to treat symptoms despite limited evidence supporting cannabis for pain, sleep, or anxiety. Given CU rates in this population, education about the risks of self-medication and the development of alternative coping strategies are needed.