Purpose: The purpose of this study was to explore the effects of medical masks on the voice quality of patients with voice disorders. Method: We included 106 patients diagnosed with voice disorders. Among them, 59 were diagnosed with vocal-fold benign lesions, 27 with insufficient glottis closure, and 20 with precancerous lesions/early-stage glottic carcinoma. Perceptual parameters (GRBAS [grade, roughness, breathiness, asthenia, strain] scale), acoustic parameters (f[subscript o], sound pressure level [SPL], jitter, shimmer, noise-to-harmonic ratio [NHR], and cepstral peak prominence [CPP]), and maximum phonation time (MPT) without and with medical masks were analyzed. Changes in the GRBAS scale after wearing medical masks were also evaluated. Results: With medical mask wearing, the G, R, and B scales in the vocal-fold benign lesion and insufficient glottic closure groups decreased, with a statistical significance seen in the G and R scales of the vocal-fold benign lesion group (G 1.07 ± 0.59, 0.95 ± 0.68, p < 0.01; R 1.07 ± 0.59, 0.95 ± 0.68, p < 0.01). The B scale in the precancerous lesions/early-stage glottic carcinoma (95%) and vocal-fold benign lesion groups (83%) and R scale in the insufficient glottic closure group (77.8%) were stable with mask wearing. f[subscript o] and SPL in the vocal-fold benign lesion group and f[subscript o] and jitter in the insufficient glottic closure group increased significantly with medical masks. The NHR and CPP in each group changed little, and all the parameters in the precancerous lesions/early-stage glottic carcinoma group showed no significant change. Conclusions: The effects of medical masks on the voice quality of patients with voice disorders were associated with the type of the disease, degree of hoarseness, and subjective scale influencing specific voice disorder. When wearing medical masks, the pitch and loudness of patients increased as compensation. Medical masks had the least impact on the precancerous lesions/early-stage glottic carcinoma group.