For youth with chronic pain, anxiety and depression are reported as consequences of experiencing pain and maintaining factors of ongoing pain and disability. However, prevalence estimates of anxiety and depression remain unclear. To report the prevalence of clinical anxiety and depression for youth with chronic pain and compare symptoms of anxiety and depression between youth with and without chronic pain. MEDLINE, PsycINFO, CENTRAL, and Embase from inception to April 30, 2023. Included studies that reported prevalence data or symptom scores for anxiety and/or depression in individuals younger than 25 years (mean, ≤18 years) with chronic pain and were published in English. From 9648 nonduplicate records, 801 full-text articles were screened. Screening and data extraction occurred in duplicate. Prevalence was determined using event rate calculations. Between-group symptom differences were calculated using Hedges g. Analyses were conducted using the random-effects model. Reporting bias and Grading of Recommendation, Assessment, Development, and Evaluation assessments were conducted. Prevalence of anxiety and depression (based on diagnosis and clinical cutoff scores) and differences in anxiety and depression symptoms. Moderators of prevalence and symptom differences were analyzed when data allowed. A total of 79 studies were included with a total sample of 22 956 youth (n = 12 614 with chronic pain). Most youth were female (mean, 74%), with an age range of 4 to 24 (mean [SD], 13.7 [2.10]) years. The prevalence estimate of anxiety diagnoses was 34.6% (95% CI, 24.0%-47.0%) and the portion that exceeded clinical cutoff scores was 23.9% (95% CI, 18.3%-30.6%). The prevalence of depression diagnoses was 12.2% (95% CI, 7.8%-18.7%) and the portion that exceeded clinical cutoff scores was 23.5% (95% CI, 18.7%-29.2%). Youth with chronic pain had greater symptoms of anxiety (g = 0.61; 95% CI, 0.46-0.77) and depression (g = 0.74; 95% CI, 0.63-0.85) compared with controls. Sex, age, pain location, and recruitment sample may moderate anxiety and depression. Considerable heterogeneity was reported for all outcomes. Studies had a low reporting bias, and outcomes were moderate to high quality. The findings of this meta-analysis suggest that 1 in 3 youth with chronic pain meet criteria for anxiety disorder, and 1 in 8 meet criteria for a depressive disorder. This represents a major clinical comorbidity. Moving forward, screening, prevention, and treatment of mental health should be important health care priorities for youth with chronic pain.