Aims: To investigate the effectiveness of a novel jaw-opening–force measuring device as a screening tool to aid in the diagnosis of temporomandibular disorders (TMD). Methods: Symptomatic TMD patients (n = 58) and control TMD-free participants (n = 56) were screened by an oral medicine specialist according to the Diagnostic Criteria for TMD (DC/TMD). TMD patients were divided into three subcategories based on TMD symptoms (myofascial pain, disc displacement, and both combined). Jaw-opening forces were measured in both groups with an adjustable head device connected to a 1,000-N–load cell. Seven attempts were recorded at 10-second intervals by a data-capturing system. The geometric mean force values were obtained after discarding the first and last attempts. Results: TMD-free participants had greater jaw-opening forces than TMD patients both without and with adjustments for age, sex, height, and weight (both P .001). The geometric mean ± standard deviation values for TMD patients were 18.5 ± 1.62 N and 47.7 ± 1.53 N for TMD-free participants. Differences in jaw-opening forces among the three TMD subcategories were not statistically significant; however, patients with disc displacement (23.7 ± 1.46 N) had greater jaw forces than patients with myofascial pain (17.0 ± 1.74 N) and both myofascial pain and disc displacement (17.0 ± 1.56 N). Conclusion: This study demonstrated that differences in jaw-opening forces could be used as a diagnostic tool for TMD. Future studies should explore the potential of this device to measure improvement in jaw-opening forces following Keywords: diagnostic tool, jaw-opening forces, myofascial pain, temporomandibular disorders, temporomandibular joint