Purpose/Objective: To examine potential differences in cognitions and traitlike factors that relate to stress among individuals diagnosed with rheumatoid arthritis (RA) compared to those with chronic pain (CP). Research Method/Design: A cross-sectional study was conducted with participants recruited from outpatient rheumatology and CP clinics. Participants completed self-report questionnaires of demographics, disease characteristics, cognitions, and traitlike constructs. Correlates of patient stress were considered using hierarchical multiple regression. Results: Analyses included 445 participants: 226 patients diagnosed with RA and 229 patients diagnosed with CP. In participants with RA, excessive worrying and anxiety sensitivity were independently associated with feeling stressed (p < .001), and 29% of the variance in stress scores was explained after adjusting for age, gender, years of education, and average pain intensity. In participants with CP, fear of relaxation, anxiety sensitivity, and pain catastrophizing were independently associated with feeling stressed (p < .001), and 31% of variance in stress scores was explained after adjusting for age, gender, years of education, and average pain intensity. Comparison of the fit of the model in both groups of patients through use of Fisher’s z test found that the set of variables did similarly well for both patients with RA and those with CP, with no significant difference between R2 values (z = .88, p = .388). Conclusions/Implications: This study establishes cognitions and traitlike factors that are related to reports of stress among patients with RA and CP. These factors should be considered when treating and developing interventions for patients who experience increased feelings of stress.