Background The objective of this study was to explore the psychometric properties of the Mouth Handicap in Systemic Sclerosis (MHISS) specifically exploring aspects of validity and reliability of MHISS in UK SSc patients. Methods A total of 150 questionnaires were distributed in this study at the Oral Medicine Department of UCLHT Eastman Dental Hospital, the Outpatient Rheumatology Clinic of the Royal Free Hospital and Scleroderma Family Day. Participants were asked to complete three questionnaires (SF-36, OHIP-14 and MHISS) along with a pro forma of demographic and disease-specific questions. Both convergent validity and internal consistency reliability were examined. The convergent validity was assessed by Spearman's correlation coefficient, and internal consistency reliability was assessed by Cronbach's alpha. Results Of the 150 questionnaires distributed to participants, 68 respondents were included. With regard to construct validity, a low to moderate degree of convergent validity was found between MHISS total score and all SF-36 subscales. However, the total MHISS score was highly correlated to all OHIP subscales. Conclusion MHISS questionnaire is a self-administered patient-reported outcome measure that assesses the mouth disability in SSc patients. However, improving the global and oral health of SSc patients is important as there is no cure for the disease; thus, instruments that record the impact of the condition and indicate the effect of treatment on the lives of patients are of paramount importance. Current results demonstrate good preliminary psychometric properties (validity and reliability) in a UK population with further exploration of psychometric properties with an emphasis on interpretability required.