Pain is the commonest symptom in cancer patients, whereas inflammation is implicated in cancer development and progression. The relationship between pain and inflammation in cancer is therefore of interest; however, it is challenging to examine because multiple factors may affect these variables. This study assessed the relationship between cancer pain and systemic inflammation using a retrospective analysis of 2 clinical trial datasets of patients with cancer cachexia. Included patients had gastrointestinal, lung, or pancreatic cancer. Pain was assessed using the pain subscale of the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire C-30. Inflammation was assessed using C-reactive protein (CRP). A regression analysis between pain and logarithmically transformed CRP was run, and Pearson correlation coefficients were calculated. A total of 718 patients entered the trials, of whom 449 had CRP measured. Both trial populations were well matched. Pain positively correlated with CRP. The Pearson correlation coefficients were 0.126 and 0.163 for trials 1 and 2, respectively. This correlation was statistically significant at the P < .05 level. These findings support that pain is related to systemic inflammation in a cohort of cancer patients. Many factors can affect pain and inflammation in cancer, demonstrating that any relationship that exists between pain and inflammation is of interest. This is in keeping with work showing this relationship in nonmalignant pain. Studies targeting inflammation and assessing its effect on pain in cancer would be an important step in the research agenda.