The purposes of this descriptive study were to describe and compare the levels of pain intensity perceived by both patients with cancer and their caregivers, and to describe a group of influencing factors contributing towards pain perception. A total of 98 dyads of patients with cancer and their caregivers from five hospitals in southern Thailand participated in this study. A pain numeric rating scale, knowledge, attitude, interrelationship between patients and caregivers, and a demographic questionnaire were used in the study. The results indicated that the overall mean pain intensity score perceived by patients and caregivers were at the mild level and moderate levels respectively. Pain intensity perceived by the patients and family caregivers was not significantly different. Hierarchical regression analysis of the patients' data sets revealed that the demographic variables, patient-caregiver relationships, and patients' knowledge and attitudes accounted for 6% of the perception of pain intensity (adjusted R2 = .06) while for the caregivers it was 21% of their perception of pain intensity (adjusted R2 = .21). The most significant factor for patients was their knowledge of cancer pain but for the caregivers' they were their relationship, education and knowledge. These findings have implications for nursing practice in planning interventions to educate cancer patients and caregivers concerning cancer pain. In addition, the contribution of the relationship between patients and caregivers suggests that nurses may need to support and strengthen this relationship.