To evaluate the outcomes of transoral laser microsurgery (TLM) for T1 glottic carcinoma using longitudinal voice analysis. Retrospective analysis of medical records. We conducted a retrospective review of 57 patients (50 T1a, seven T1b) who underwent TLM for T1 glottic carcinoma, and longitudinal voice analysis was performed before surgery, during the early postoperative period (within 3 months), and during the late postoperative period (more than 6 months). Acoustic, perceptual (Grade, Roughness, Breathiness, Asthenia, Strain scale), and subjective voice analysis using the Voice Handicap Index (VHI) was conducted. Voice quality deteriorated in the early postoperative period in terms of several parameters. However, no significant differences in voice quality were observed in the late postoperative period, whereas Grade (from 1.85 ± 0.83 to 1.50 ± 0.90) and Roughness (from 1.74 ± 0.73 to 1.48 ± 0.87) had improved significantly. Patients who underwent lesser-extent cordectomy (type I, II) showed improvement in VHI-Physical (from 12.93 ± 11.10 to 6.07 ± 8.69) and Grade (from 1.60 ± 0.68 to 0.98 ± 0.83), whereas improvement was not identified in those who underwent larger-extent cordectomy (type III, IV, V). Improvement in Grade (from 1.70 ± 0.80 to 1.23 ± 0.91) and Roughness (from 1.77 ± 0.73 to 1.25 ± 0.76) was identified in patients who had unilateral tumor without involvement of anterior commissure. However, those with involvement of the anterior commissure or bilateral vocal cord showed a tendency toward deterioration in voice quality. Voice quality of patients following TLM for T1 glottic carcinoma may improve significantly over time in cases with lesser-extent types of cordectomy or unilateral tumor without involvement of the anterior commissure. 4 Laryngoscope, 126:2051-2056, 2016.