In chronic musculoskeletal pain patients, early prevention and detection for musculoskeletal dysfunction (i.e., sarcopenia) is an issue of significant clinical interest. Phase angle, which can be measured through bioelectrical impedance analysis, can detect sarcopenia; however, the evidence on chronic musculoskeletal pain patients is limited. This study aimed to assess the relationship between phase angle and sarcopenia in patients with chronic musculoskeletal pain. A total of 190 patients (51 men, 139 women; mean age: 67.2 years) with chronic musculoskeletal pain were included in this retrospective cross-sectional study. Sarcopenia was diagnosed using the Asian Working Group for Sarcopenia Criteria 2019. A total of 51 patients (26.7%) including 10 men (19.6%) and 41 women (29.5%) were diagnosed with sarcopenia. Phase angle, sarcopenia-related factors, age, and BMI differed significantly in patients with and without sarcopenia. On multiple logistic regression analysis, the prevalence of sarcopenia was observed to be significantly correlated with phase angle and BMI. The areas under the curve exhibited high accuracy in discriminating sarcopenia in men and moderate accuracy in both genders and in women. We conclude that phase angle may be a useful tool for detecting sarcopenia in the patients with chronic musculoskeletal pain.