The present study aimed to examine the acceptability, feasibility, and preliminary effectiveness of an older peer and clinician co-facilitated Behavioral Activation for Pain Rehabilitation (BA-PR) intervention among adults aged 50 years and older with comorbid chronic pain and mental health conditions. This was a mixed-methods research design with eight participants aged 55 to 62 years old with mental health conditions including schizophrenia spectrum disorder, bipolar disorder, major depressive disorder, personality disorder, and adjustment disorder. The quantitative data were assessed from observational methods, a pain rating scale and related measures. We used semi-structured interviews for qualitative feedback on experiences with the BA-PR intervention after participation. Overall, the participants had positive experiences following receipt of the BA-PR intervention. The recruitment and adherence rates for participants were 72.7% and 100%, respectively. Approximately 75% of the participants remained enrolled in the study. Findings from a paired t-test showed the BA-PR intervention was linked to significantly reduced prescription opioid misuse risk, t (7) = 2.42, p < 0.05. There were also non-significant reductions in pain intensity and depression severity, in addition to improvements in active and passive pain coping strategies and behavioral activation.The BA-PR intervention is the first pain rehabilitation intervention specifically designed for middle-aged and older adults with comorbid chronic pain and mental health conditions. Our findings indicate promise for the BA-PR intervention to potentially reduce prescription opioid misuse risk, pain, and depressive symptoms. However, a quasi-experimental study is needed before rigorous effectiveness testing.