Background/Objectives: Parkinson's disease (PD) is a progressive neurodegenerative disorder characterised by motor and non-motor symptoms, including pain. Temporomandibular disorder (TMD)-like pain, defined as self-reported pain modified by jaw activities, has been suggested to be more prevalent in PD, but its association with PD severity remains unclear. This study aimed to investigate the association between pain modified by jaw activities and PD severity and the temporal stability of such pain in PD. Methods: This prospective study recruited 28 individuals with PD. Motor symptom severity and disability levels were evaluated using the modified Hoehn and Yahr (mHY) staging and modified Rankin Scale (mRS), respectively. Based on the diagnostic criteria for TMD, a questionnaire assessing pain modified by jaw activities and clinical examination were utilised. Pain modified by jaw activities was reassessed at one, two, and three months. Statistical analyses included Spearman's rank correlation test and Friedman test, with p < 0.05 considered significant. Results: The participants' mean age was 69.2 ± 9.6 years; 53.6% were male. Eight participants reported pain modified by jaw activities. Clinical examination identified painful palpation sites in 14 participants, most commonly in the masseter muscle body. Pain modified by jaw activity count showed significant positive correlations with mHY stage (rho = 0.48, p = 0.015) and mRS score (rho = 0.41, p = 0.04). Twenty-four participants completed follow-up, with no significant changes in pain reports over three months. Conclusions: Some individuals with PD may experience persistent TMD-like pain, which is correlated with motor symptom severity and disability levels, highlighting the importance of routine TMD screening in PD.