OBJECTIVE Negative affectivity and social isolation (Type D personality) are personality traits associated with poor health-related quality of life (HRQoL). We hypothesized these traits would be associated with impaired HRQoL and increased gastrointestinal symptom severity in functional gastrointestinal disorders. METHODS Data were collected from patients undergoing breath testing. Patients completed the Type D Scale-14, Gastrointestinal Symptoms Severity Index and Short-Form Health Survey 12. RESULTS Of 230 patients evaluated, 37% met criteria for Type D personality. Type D was associated with a decreased Mental Component score on the Short-Form Health Survey 12 (mean difference = -8.29; 95% confidence interval, 5.2-11.4; P < .001). On the Gastrointestinal Symptoms Severity Index, severity of symptoms was significantly higher in Type D patients compared with non Type D patients (P < .001). CONCLUSIONS Type D personality was associated with decreased perceived HRQoL and reporting of more severe gastrointestinal symptoms. Type D personality construct may be an important consideration when assessing HRQoL outcomes. Consideration of personality traits could improve risk stratification in research and clinical practice in this patient group.