Objective <p>This study aimed to assess the feasibility of handheld ultrasound for scanning and measuring masseter muscle thickness.</p> Methods <p>This prospective pilot study included adult participants aged 18 and older. Inclusion criteria specified healthy individuals without pain or a TMD diagnosis in the last six months and not receiving neuromodulators as a treatment for TMJ-related issues. Exclusion criteria included individuals with developmental disorders affecting the craniofacial skeleton or with connective tissue and dermatological disorders impacting skin thickness. A scanning protocol was developed for a new handheld ultrasound system [4–12 MHz; (Lumify, Philips, USA)] to assess the masseter muscle thickness of participants in relaxed and clenched states.</p> Results <p>Two evaluators analyzed ninety-two ultrasound scans from 12 participants. Intraclass correlation coefficient and standard deviations between the observers were calculated. Reliability for masseter measurements ranged from good to excellent (ICC 0.84–0.93) for Intra-observer and excellent for Inter-observer (ICC 0.93–0.98).</p> Conclusion <p>The preliminary findings of this study demonstrate the high reliability of handheld ultrasound in assessing masseter muscle. The results support the use of handheld ultrasound to assess masseter muscle thickness. This system can be an alternative to cart-based systems facilitating the implementation of ultrasound as a chair-side tool in dentistry.</p>