Background: As the population ages, the number of people with chronic diseases increases. Frequently, older people suffer from joint pain together with other chronic diseases, which can lead to decreased physical functioning. Aims: To investigate the associations of the changes in cognitive appraisals, coping strategies and pain with the change in physical functioning in older people, who have chronic pain and chronic diseases. Methods: Elderly persons (n = 407, mean age 77 years, and 62% female), with self-reported joint pain and at least two chronic diseases, filled in questionnaires about cognitive appraisals, coping strategies, pain intensity and physical functioning at baseline, at 6- and 18-month follow-ups. The associations of change in physical functioning with changes in cognitive appraisals, coping strategies and pain were modelled using generalized estimating equations (GEE). Results: Increase in pain, in negative thinking about the consequences of pain, and in activity avoidance and decrease in self-efficacy beliefs were associated with a decline in physical functioning. Discussion: Observed mean changes were small but large inter-individual variability was seen. This shows that cognitive appraisals and coping strategies are malleable. Statistical model of change clarifies the direction of longitudinal associations. Conclusions: The longitudinal findings suggest that joint pain, cognitive appraisals and coping strategies may determine physical functioning in older people who have chronic pain and comorbidity.