Introduction Type D (distressed) personality is defined as the co-occurrence of negative affect (NA) and social inhibition (SI). Objectives Although many studies have analyzed the association of irritable bowel syndrome (IBS) and personality traits, the effect of Type D personality on sleep quality of patients with IBS has not been evaluated. Aims We aimed to assess the prevalence of Type D personality in patients with and to investigate whether the presence of a Type D personality would affect subjective sleep quality in patients with IBS. Methods Ninety-seven patients who met the Rome III criteria for IBS with no psychiatric comorbidity were consecutively enrolled, along with 39 healthy controls. Type D Scale, Pittsburgh Sleep Quality Index (PSQI), and Hospital Anxiety and Depression Scale were used in the collection of data. Results Of 97 patients evaluated, 45.4% met criteria for Type D personality. Thirty-five patients (36.1%) and 7 healthy volunteers (17.9%) were “poor” sleepers (p Conclusion Type D personality was associated with decreased perceived sleep quality in patients with IBS.