Medical debt is common in the US and may hinder timely access to care for mental disorders. To estimate the prevalence of medical debt among US adults with depression and anxiety and its association with delayed and forgone mental health care. Cross-sectional, nationally representative survey study of US adult participants in the 2022 National Health Interview Survey who had current or lifetime diagnoses of depression or anxiety. Self-reported lifetime clinical diagnoses of depression and anxiety; moderate to severe symptoms of current depression (Patient Health Questionnaire-8 score ≥10) and anxiety (Generalized Anxiety Disorder-7 score ≥10) irrespective of lifetime diagnoses; and past-year medical debt. Self-reported delaying and forgoing mental health care because of cost in the past year. Among 27 651 adults (15 050 [54.4%] female; mean [SD] age, 52.9 [18.4] years), 5186 (18.2%) reported lifetime depression, 1948 (7.3%) reported current depression, 4834 (17.7%) reported lifetime anxiety, and 1689 (6.6%) reported current anxiety. Medical debt was more common among adults with lifetime depression (19.9% vs 8.6%; adjusted prevalence ratio [aPR], 1.97; 95% CI, 1.96-1.98), lifetime anxiety (19.4% vs 8.8%; aPR, 1.91; 95% CI, 1.91-1.92), current depression (27.3% vs 9.4%; aPR, 2.34; 95% CI, 2.34-2.36), and current anxiety (26.2% vs 9.6%; aPR, 2.24; 95% CI, 2.24-2.26) compared with adults without the respective mental disorders. Medical debt was associated with delayed health care among adults with lifetime depression (29.0% vs 11.6%; aPR, 2.68; 95% CI, 2.62-2.74), lifetime anxiety (28.0% vs 11.5%; aPR, 2.45; 95% CI, 2.40-2.50), current depression (36.9% vs 17.4%; aPR, 2.25; 95% CI, 2.13-2.38), and current anxiety (38.4% vs 16.9%; aPR, 2.48; 95% CI, 2.35-2.66) compared with those without these diagnoses. Medical debt was associated with forgone health care among adults with lifetime depression (29.4% vs 10.6%; aPR, 2.66; 95% CI, 2.61-2.71), lifetime anxiety (28.2% vs 10.7%; aPR, 2.63; 95% CI, 2.57-2.68), current depression (38.0% vs 17.2%; aPR, 2.35; 95% CI, 2.23-2.48), and current anxiety (40.8% vs 17.1%; aPR, 2.57; 95% CI, 2.43-2.75) compared with those without the diagnoses. Medical debt is prevalent among adults with depression and anxiety and may contribute to the mental health treatment gap. In the absence of structural reform, new policies are warranted to protect against this financial barrier to mental health care.