This study aimed to test the cross-sectional mediating and moderating role that positive psychological factors play in the association between pain intensity and pain interference in individuals with chronic musculoskeletal pain. A descriptive cross-sectional study using mediation analyses was conducted, including 186 individuals with chronic musculoskeletal pain. We conducted cross-sectional mediation and moderation analyses to determine whether the positive psychological factors mediated or moderated the association between pain intensity and pain interference. Pain acceptance, pain self-efficacy, and optimism were all significantly and weakly related to pain interference when controlling for pain intensity. Pain self-efficacy and pain acceptance partially mediated the association between pain intensity and pain interference. On the other hand, the multiple mediation model did not show significant effects. The three positive psychological factors were not found to significantly moderate the association between pain intensity and pain interference. The findings suggest that in chronic musculoskeletal pain patients, the treatments may focus on [i] what they are capable of doing to manage the pain (i.e., pain self-efficacy) and [ii] being better able to accept the pain as pain waxes and wanes might be also particularly helpful. However, these results must be tested in longitudinal studies before drawing any causal conclusion.