Aims: To assess the degree and interrelationship of sleep disturbance and plasma cytokine levels in temporomandibular disorder (TMD) pain patients. Methods: Forty female TMD patients and 20 age-, sex-, and body mass index (BMI)-matched healthy subjects were enrolled. TMD was diagnosed using the Research Diagnostic Criteria for TMD. The TMD patients were classified as having low or high disability according to Graded Chronic Pain Scale findings. The Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS) were used to measure sleep quality. Plasma concentrations of interleukin (IL)-1β, IL-6, IL-10, tumor necrosis factor-α (TNF-α), and C-reactive protein (CRP) were measured from blood samples collected between 9 am and noon. Statistical analyses included Kruskal-Wallis and one-way analysis of variance tests to compare results between different groups and multivariate general linear models to evaluate the effect of sleep status on cytokine levels. Results: The highdisability group had the highest PSQI and ESS scores (P .001). Plasma levels of IL-1β, IL-6, IL-10, and TNF-α were significantly higher in the patient groups, with the high-disability group exhibiting the highest values (P ≤ .001). The plasma cytokine levels were significantly correlated with PSQI scores (P .05). Plasma levels of IL-10 and TNF-α were significantly associated with the disability level after adjusting for both sleep indices (both P .05). Conclusion: Patients with TMD, especially those with high disability, had elevated plasma cytokine levels and increased ESS and PSQI scores suggestive of sleep disturbance. Keywords: cytokine level, pain, sleep disturbance, temporomandibular disorders