The COVID-19 pandemic prompted unexpected changes in the healthcare system. This current longitudinal study had two aims: 1) describe the trajectory of pandemic-associated stressors and patient-reported health outcomes among patients receiving treatment at a tertiary pain clinic over two years (May 2020 to June 2022); and 2) identify vulnerable subgroups. We assessed changes in pandemic-associated stressors and patient-reported health outcome measures. The study sample included 1,270 adult patients who were predominantly female (74.6%), White (66.2%), non-Hispanic (80.6%), married (66.1%), not on disability (71.2%), college-educated (59.45%), and not currently working (57.9%). We conducted linear mixed effect modeling to examine the main effect of time with controlling for a random intercept. Findings revealed a significant main effect of time for all pandemic-associated stressors except financial impact. Over time, patients reported increased proximity to COVID-19, but decreased pandemic-associated stressors. A significant improvement was also observed in pain intensity, pain catastrophizing, and PROMIS-pain interference, sleep, anxiety, anger, and depression scores. Demographic-based subgroup analyses for pandemic-associated stressors revealed that younger adults, Hispanics, Asians, and patients receiving disability compensation were vulnerable groups either during the initial visit or follow-up visits. We observed additional differential pandemic effects between groups based on participant sex, education level, and working status. In conclusion, despite unanticipated changes in pain care services during the pandemic, patients receiving pain treatments adjusted to pandemic-related stressors and improved their health status over time. As the current study observed differential pandemic impacts on patient subgroups, future studies should investigate and address the unmet needs of vulnerable subgroups. PERSPECTIVE: Over a two-year timeframe, the pandemic did not adversely influence physical and mental health among treatment-seeking patients with chronic pain. Patients reported small but significant improvements across indices of physical and psychosocial health. Differential impacts emerged among groups based on ethnicity, age, disability status, gender, education level, and working status.