In this paper, gender dysphoria is presented in the context of phonetics, and the most important approaches to voice feminization and masculinization are listed. Based on speech material before and after vocal therapy in the duration of 13 sessions, an acoustic analysis was made. As part of the acoustic analysis, acoustic parameters such as fundamental frequency, jitter, shimmer, HNR and formant values were analyzed, and long-term average voice spectra based on reading non-fricative text and free speech were examined. The voice was assessed aurally, and the completed self-assessment questionnaires were also taken into account. Additionally, the paper contains a methodical component, where the approach to working with a transgender woman was presented through a work diary. By comparing the results before and after vocal therapy, several observations were made: a slight increase in the formant frequency, an increase in the fundamental frequency, a brighter color of the voice caused by a change in resonance, more pronounced intonation patterns and a shortening of the phonation time. The long-term average spectrum of the voice shows a balancing of the spectrum in its central parts and an increase in intensity in the area of higher brilliance. After vocal therapy, the voice was assessed as more feminine.