BACKGROUND: Per the biopsychosocial model, pain, especially chronic low back pain, which often presents with nonspecific pain, requires a comprehensive approach involving social factors. However, the association of social factors, including social isolation and loneliness, with this condition remains unclear. This study examined the cross-sectional association of social isolation and loneliness with chronic low back pain among older adults. METHODS: We recruited functionally independent older adults through a mail survey in 2019 from the Japan Gerontological Evaluation Study (JAGES). Chronic low back pain was defined as low back pain lasting more than 3 months. Social isolation was identified based on face-to-face and non-face-to-face interactions ("not isolated," "isolated tendency," and "isolated"). Loneliness was assessed using the University of California, Los Angeles Loneliness Scale ("not lonely," "lonely tendency," and "lonely"). RESULTS: Consequently, 21,463 participants were analyzed (mean age: 74.4 years; 51.5% females); 12.6% reported chronic low back pain. Multivariable Poisson regression analysis revealed that loneliness was significantly associated with the likelihood of chronic low back pain; compared with "not lonely", the prevalence ratio (PR) was 1.14 (95% confidence interval [CI], 1.05-1.25) for "lonely tendency" and 1.40 (95% CI, 1.27-1.54) for "lonely." Social isolation was not associated; compared with "not isolated," the PR was 0.96 (95% CI, 0.88-1.05) for "isolated tendency" and 0.99 (95% CI, 0.89-1.10) for "isolated." A positive multiplicative interaction between social isolation and loneliness for chronic low back pain was found. CONCLUSION: Lonelier individuals were more likely to experience chronic low back pain, and those with loneliness and social isolation were synergistically more likely for this condition.