Aims: To evaluate salivary levels of the proinflammatory cytokine interleukin- 1β (IL-1β) in patients with temporomandibular disorders (TMD), fibromyalgia, or both conditions in comparison to healthy individuals. Methods: A total of 69 females (18 to 84 years of age) were assigned to one of four groups: (A) healthy controls (n = 27); (B) TMD only (n = 18); (C) fibromyalgia only (n = 15); and (D) fibromyalgia plus TMD (n = 9). Clinical data and salivary IL-1β levels were evaluated. Statistical analysis was performed by using Fischer exact test, unpaired Student t test, or one-way analysis of variance plus multiple comparisons Tukey test, depending on the variable. The correlation between age and IL-1β levels was assessed by using Pearson correlation coefficient. Results: Most patients in groups B and D displayed clinical features of Group I (muscle disorders) and Group II (disc displacements) of the Axis I Research Diagnostic Criteria for Temporomandibular Disorders. The subjects in groups C and D presented values of > 7 on the Widespread Pain Index (WPI) and > 5 for Symptom Severity Score (SS) according to the Fibromyalgia Survey Diagnostic Criteria and Severity Scale. There were no significant differences when SS and WPI levels were compared between groups C and D. The patients with TMD showed significantly higher salivary IL-1β levels irrespective of a fibromyalgia diagnosis (groups B and D), whereas the fibromyalgia-only patients (group C) did not show any significant difference in relation to controls. Conclusion: This study provides novel evidence indicating that salivary IL-1β may be a biomarker for TMD.