The aim of the present study was to investigate the correlation between the chronicity of myogenous temporomandibular disorder (TMD) and skin temperature over the masseter and anterior temporalis muscles. A blind, cross-sectional study was carried out involving 30 women with myogenous TMD, aged 18 to 40 years (mean of 23.60 ± 5.12 years). The volunteers were recruited from the university community. The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) was used for the diagnosis of TMD and the determination of chronicity. The volunteers were also submitted to infrared thermography to measure absolute skin temperature over the masseter and anterior temporalis muscles and determine their temperature asymmetries. A significant association was found between duration of TMD and temperature asymmetry of the anterior temporalis muscle (rs = 0.224, p = 0.034). The present findings demonstrate that chronicity of myogenous TMD changes the skin temperature over the anterior temporalis muscle.