Background: Some studies suggest that oral behaviours, such as clenching, grinding and nail biting, are common in patients with temporomandibular disorders (TMDs). However, the relationship between oral behaviours and key aspects of TMDs, such as pain‐related disability, remains unexplored.

Study Objective: The study aimed to assess the relationship between oral behaviours and pain in TMD patients with low or high pain–related disability, compared to pain‐free individuals without TMD (non‐TMD).

Methods: In this cross‐sectional study, adult participants who attended the dental unit at the University of Trieste, Italy, between January 2018 and June 2021 were asked to complete the oral behaviour checklist (OBC) and graded chronic pain scale (GCPS). OBC total score and item scores were compared between TMD patients with low pain–related disability, TMD patients with high pain–related disability and pain‐free individuals without TMD, using one‐way ANOVA with Bonferroni‐adjusted pairwise comparisons.

Results: A total of 1581 patients participated, of whom 1304 were pain‐free, 234 were TMD patients with low pain–related disability and 43 were TMD patients with high pain–related disability. Average OBC total scores were 12.2 ± 8.8 for pain‐free non‐TMD participants, 17.2 ± 10.9 for TMD patients with low pain–related disability and 23.16 ± 12.15 for TMD patients with high pain‐related disability. Significant differences were found across all pairwise comparisons ( p  < 0.001). Specific oral behaviours, such as awake and sleep‐related clenching, were notably higher in both TMD groups compared to the pain‐free group.

Conclusion: A significant association between pain‐related disability and oral behaviours in TMD patients has been demonstrated.