Background: Myofascial pain syndrome (MPS) is a condition that involves skeletal muscles. It is caused by overload or disuse of muscles and is characterized by extreme tenderness in the muscles with taut bands. Treatment for MSP is different from that for cancer-related pain. Cancer patients have many factors that cause restriction of body movement and posture. Although cancer patients appear to demonstrate risk factors for MPS, its prevalence has not been reported in patients with incurable cancer. This study was conducted to investigate the prevalence of MPS in patients with incurable cancer. Methods: The data for patients with incurable cancer who received palliative care by our department between September 2015 and March 2016 were retrospectively investigated. We examined the prevalence of MPS. MPS was diagnosed on the basis of the Rivers criteria (RC) and Simons criteria (SC). We also examined the following factors associated with MPS: performance status (PS), use of medical devices (MD), and primary cancer sites. The primary outcome was the prevalence of MPS using the RC. Secondary outcomes included the prevalence of MPS using the SC, and the relationship between MPS and either PS or MD. Results: Thirty-four patients with incurable cancer were identified. The clinical characteristics are as follows: age (median, range): 65 (39-89) years; male/female ratio: 16/18; primary sites: pancreas (n = 8), breast (n = 8), lung (n = 4), colorectal (n = 4), head and neck (n = 2), and other primary sites (n = 8). Seventeen of 34 patients (50%) had a PS 3 or 4. Twenty-two patients (64.7%) complained of pain. MPS using the RC was detected in 10 patients (29%). MPS using the SC was detected in 20 patients (59%). Of 22 patients who complained of pain, MPS using the RC was detected in 10 (45%) patients and MPS using the SC was detected in 20 (90%) of patients. Patients with central venous port (CVP) devices had a significantly higher number of MPS lesions than patients without CVP devices (p = 0.029). Conclusions: A very high prevalence of MPS was detected in our study population. MPS should be considered when patients with incurable cancer complain of pain. A multi-center prospective study will be conducted to confirm our findings.