The main object of this study is to investigate whether emotional alteration, and specifically stress, is associated with activity reduction and the impact on the lives of people with chronic pain. We worked with a sample of 92 subjects with chronic pain. All of them were patients at the Pain Unity of the University Hospital “San Cecilio” of Granada, Spain. Our results confirm the significant differences among subjects with high and low levels of stress in the degree of pain interference with activity and daily functioning. No differences were found in function of age in the studied variables, although men with chronic pain showed greater levels of stress than women. From the studied dimensions, the activity reduction in function of the interference that chronic pain causes in life, and emotional affectation, among others, predicted more stress. A possible relationship model among the studied variables is discussed, as well as practical implications.