Objective: Autism, attention deficit hyperactivity disorder (ADHD), and tic disorder (Tourette syndrome; TS) are neurodevelopmental conditions that frequently co-occur and impact psychological, social and emotional functioning. Vulnerability to chronic physical symptoms, including fatigue and pain, are also recognised. The expression of joint hypermobility, reflecting a constitutional variant in connective tissue, predicts vulnerability to psychological symptoms alongside recognised physical symptoms. Here, we tested for increased rates of joint hypermobility, autonomic dysfunction and pain in 109 adults with neurodevelopmental diagnoses. Method: Rates of generalized joint laxity in those individuals with neurodevelopmental conditions were compared to those in the general population in UK. Levels of orthostatic intolerance and musculoskeletal symptoms were compared to a neurotypical control group. Results: Adults with neurodevelopmental diagnoses manifest elevated rates of joint hypermobility (50%) compared to the general population rate of 20% and a matched control population of 10%. Odds ratio for hypermobility in individuals with neurodevelopmental diagnoses, compared to the general population was 4.51 (95%CI 2.17-9.37), with greater odds in females rather than males. Neurodevelopmental patients reported significantly more symptoms of orthostatic intolerance and musculoskeletal skeletal pain than controls Conclusions: In adults with neurodevelopmental conditions, there is a strong link between the expression of joint hypermobility, autonomic dysfunction and pain, more so than in healthy controls. Increased awareness and understanding of this association may enhance the management of core symptoms and allied difficulties including comorbid stress-sensitive physical symptoms.