Previous research suggests that individuals with mental health needs and chronic pain may be less likely to use mental health treatment compared with those with mental health needs only. Yet, few studies have investigated the existence of population-level differences in mental health treatment use. We analyzed data from the National Health Interview Survey (n = 31,997) to address this question. We found that chronic pain was associated with end-to-end disparities in the mental health journeys of U.S. adults: (1) Those living with chronic pain are overrepresented among U.S. adults with mental health needs; (2) among U.S. adults with mental health needs, those living with chronic pain had a lower prevalence of mental health treatment use; (3) among U.S. adults who used mental health treatment, those living with chronic pain had a higher prevalence of screening positive for unremitted anxiety or depression; (4) among U.S. adults living with both chronic pain and mental health needs, suboptimal mental health experiences were more common than otherwise—just 44.4% of those living with mental health needs and co-occurring chronic pain reported use of mental health treatment and screened negative for unremitted anxiety and depression, compared with 71.5% among those with mental health needs only. Overall, our results suggest that U.S. adults with chronic pain constitute an underrecognized majority of those living with unremitted anxiety/depression symptoms and that the U.S. healthcare system is not yet adequately equipped to educate, screen, navigate to care, and successfully address their unmet mental health needs.