In chronic pain context, recent studies have begun to consider the relevance of the patient’s cognitive appraisal about their pain. Nevertheless, there are not many instruments that allow us to measure the cognitive appraisal of pain. The main purpose of this study was the development of an instrument to measure cognitive primary appraisal in chronic pain patients. First, following transactional models of stress and considering the consequences that chronic pain has in patients (e.g., loss of autonomy, threat to familiar or work roles), the items of the instrument were formulated. Principal component analysis revealed three components of primary appraisal: (1) loss or harm, (2) threat and (3) challenge. In a sample of 224 subjects with chronic pain, the three scales showed high internal consistency and criteria validity in relation to pain, coping and functioning. The Cognitive Appraisal Inventory (“Inventario de evaluación cognitiva”, IEC) appears to be a promising scale for use in future chronic pain research.