Background: There is concern that tongue protrusion may be maladaptive in individuals with Down syndrome (DS). However, tonguing and other self-manipulatory behaviours have been shown to contribute to emotion regulation in children without disabilities. Method: Sixty individuals with intellectual disability (40 with DS, 20 of mixed aetiology) and their parents were videotaped during a puzzle-book task. Empirical relationships between observed tongue protrusion, other observed nonverbal behaviours, and reported negative mood, maladaptive behaviours, and stress-inducing characteristics were assessed. Results: Individuals with DS and reported negative mood who did not engage in tonguing were more likely to display internalising and externalising behaviours and stress-inducing characteristics, whereas those who did engage in tonguing were not more likely to display these characteristics. Conclusion: These findings are consistent with the possibility that tongue protrusion serves an emotion regulation function for individuals with DS. (Contains 3 tables.)