Aims: To test whether the Neck Disability Index (NDI) would indicate higher reported disability among people with neck pain, cervicogenic headache, and temporomandibular disorders (TMD) when compared to people with only neck pain or neck pain with cervicogenic headache. Methods: A total of 62 participants were enrolled and categorized into one of three groups: (1) neck pain only; (2) neck pain and cervicogenic headache; and (3) neck pain, cervicogenic headache, and TMD. NDI scores, pain, cervical active range of motion (AROM), and maximum mouth opening (MMO) were recorded for each subject. NDI scores were compared between groups using the Kruskal-Wallis test, and associations between the NDI and pain, cervical AROM, and MMO were tested using Pearson correlations. Results: No statistical difference in NDI score was identified among the three groups (P = .08). NDI scores were not correlated with MMO (P = .17) or TMD pain (P = .16), but were correlated with cervical AROM (r = -0.635 to -0.311), cervicogenic headache intensity (r = 0.355; P = .004), and cervical pain ratings (r = 0.619; P .001) across all participants. Conclusion: Participants' perceived disabilities were not associated with TMD pain or MMO. The NDI does not seem adequate for assessing TMD symptoms. Keywords: maximum mouth opening, Neck Disability Index, outcomes, pain, temporomandibular disorders