Purpose: Teachers are occupational voice users with significant vocal demand. This study examined if a vocal hygiene program could mitigate the effects of occupational vocal demand in primary school teachers across 1 month. Method: Sixty female teachers participated, with 30 in an experimental group receiving vocal hygiene education plus daily home practice for 1 month and 30 in a control group with no intervention. Their vocal changes across the month were quantified with (a) acoustic measures on fundamental frequency (f[subscript o]), vocal intensity, jitter and shimmer, harmonics-to-noise ratio, and smoothed cepstral peak prominence and (b) Voice Handicap Index (VHI-10) and Vocal Fatigue Index (VFI) scores. Results: Analysis of covariance showed significantly larger changes (significant decreases) in conversational f[subscript o] and in jitter for the experimental group relative to the control group. Post hoc pairwise comparisons following repeated-measures analysis of variance showed significant decreases in conversational f[subscript o] and in jitter across the month for the experimental group. No significant differences in VHI-10 and VFI scores were found between the groups. Conclusions: Vocal demand-related changes in acoustic measures could be partially mitigated with the vocal hygiene program. Future studies with a more refined intervention program and more long-term follow-up are recommended to better understand the long-term benefits of vocal hygiene programs on primary school teachers.