Purpose: The purpose of this study was to examine the short- and longer-term effects (3-month follow-up) of a 1-month intensive straw phonation (SP) therapy on the voice quality and voice-related quality of life of female speech-language pathology (SLP) students with mild dysphonia. Method: Thirty-two female SLP students (mean age: 18.5 years, range: 17.8-19.8 years) with mild dysphonia were included in this study. A randomized controlled trial was used with three experimental groups and a control group. The experimental groups received a short-term intensive voice therapy of one month with SP in air (n = 8), SP in 2 cm water (n = 8) or SP in 5 cm water (n = 8). The control group (n = 8) received a comparable voice therapy by using [u] phonation with similar soft onset and slightly pursed lips as in SP but without a straw. Three maintenance sessions were provided via telepractice in the next month. A multidimensional voice assessment was performed immediately before therapy (pre), immediately after therapy (post 1) and at 1 month (after the maintenance therapy = post 2) and 3 months follow-up (post 3) by an assessor blinded to the group assignment and study phase. Results: No significant time-by-group interactions were found for any of the outcome measures, indicating no significant differences in evolution over time among the four groups. Primary outcomes: Within-group analyses showed a significant increase (improvement) in Dysphonia Severity Index (DSI) between post 1 and post 2 in the SP in 2 cm water group. Trends of improvement were visible in DSI between pre and post 1 in the SP in air group, and between pre/post 1 and post 2 in the SP in 5 cm water group. A clinically relevant decrease (improvement) in Acoustic Voice Quality Index (AVQI) was found between pre and post 1 in the SP in 2 cm water group. Secondary outcomes: Within-group analyses further showed a significant increase in the SP in 2 cm water group in the highest intensity between pre and post 1/post 2, a significant decrease in the lowest frequency between pre and post 3, and a significant decrease in Vocal Fatigue Index between pre and post 1/post 2. The SP in the air group showed an increase in the highest frequency between pre and post 2. The SP in 5 cm water group showed improvements in the auditory-perceptual parameters, roughness, and strain between pre and post 1. Conclusions: Positive effects were found for the three SP interventions. The most promising results were found for SP in 2 cm water, suggesting an optimal impedance match between the glottis and the vocal tract in this specific population of female SLP students with mild dysphonia.