In systemic sclerosis (SSc), mouth and face involvement leads to problems in oral health-related quality of life (OHRQoL). Mouth Handicap in Systemic Sclerosis scale (MHISS) is a 12-item questionnaire specifically quantifying mouth disability in SSc, organized in 3 subscales. Our aim was to validate Italian version of MHISS, by assessing its test-retest reliability and internal and external consistency in Italian SSc patients. Forty SSc patients (7 dSSc, 33 lSSc; age and disease duration: 57.27 ± 11.41, 9.4 ± 4.4 years; 22 with sicca syndrome) were evaluated with MHISS. MHISS was translated following a forward-backward translation procedure, with independent translations and counter-translation. Test-retest reliability was evaluated, comparing the results of two administrations, with intraclass correlation coefficient (ICC). Internal consistency was assessed by Cronbach's α and external consistency by comparison with mouth opening. MHISS has a good test-retest reliability (ICC: 0.93) and internal consistency (Cronbach's α:0.99). A good external consistency was confirmed by correlation with mouth opening (rho: -0,3869, p: 0.0137). Total MHISS score was 17.65 ± 5.20, with scores of subscale 1 (reduced mouth opening) of 6.60 ± 2.85 and scores of subscales 2 (sicca syndrome) and 3 (aesthetic concerns) of 7.82 ± 2.59 and 3.22 ± 1.14. Total and subscale 2 scores are higher in dSSc than in lSSc. This result may be due to the higher presence of sicca syndrome in dSSc than in lSSc (p = 0.0109). Our results support validity and reliability in Italian SSc patients of MHISS, specifically measuring SSc OHRQoL.