Background: Temporomandibular disorders (TMD) are the most common cause of non-dental orofacial pain and affect about one-third of adults. Population-based data obtained with standardized criteria are scarce in Mongolia, particularly outside the capital. Aim: To determine the prevalence of clinical signs of TMD and of examination-based Diagnostic Criteria for TMD (DC/TMD) diagnoses among residents of western Mongolia, and to compare them by sex and age group. Materials and Methods: This retrospective secondary data analysis utilized research data collected in 2020–2021 across Bayan-Ulgii, Govi-Altai, Zavkhan, Uvs, and Khovd aimags. A total of 520 participants were included in the analysis; participants aged from 16 to 71 years, with females accounting for 72.3%. Ethical approval for the secondary use of data was obtained in 2024. Diagnoses that can be established from the examination alone (IIa, IIIa–IIIc) were assigned. Differences were tested with chi-square and Fisher’s exact tests and logistic regression. The study was approved by the MNUMS Research Ethics Committee (№24/3-06) Results: At least one clinical sign was found in 87.1% of participants; deviation on opening (58.1%) and joint sounds (56.2%) were the most common. Muscle and joint pain on opening were found in 16.7% and 18.3%, and muscle and joint pain on palpation in 8.7% and 8.3%, respectively. An examination-based diagnosis was established in 21.5% (95% CI 18.2–25.3); disc displacement with reduction (14.4%) was the most common and Group III diagnoses were found in 8.3%. Pain on palpation at three or more muscle sites was found in only 3.3%. Compared with men, women more often had joint pain on opening (21.0% vs 11.1%; p=0.009) and muscle and joint pain on palpation, and had 2.5-fold higher odds of a Group III diagnosis (OR 2.50; 95% CI 1.02–6.15). Muscle pain on opening decreased with age (from 26.7% to 10.6%; p=0.036), whereas diagnoses did not differ by age group. Conclusions Most residents of western Mongolia had at least one clinical sign of TMD, mainly deviation on opening and joint sounds, and one in five had an examination-based DC/TMD diagnosis. Painful joint conditions were more common in women. The low prevalence of myofascial pain should be interpreted in light of limited standardization of palpation.