Here we have developed methods to transiently and stably transfect the human pathogenic protist Trichomonas vaginalis. The viral RNA-based transfection vector pTVV-EGFP/NEO was constructed by using enhanced green fluorescent protein gene (EGFP) and neomycin resistance gene (NEO) in tandem to replace the whole gene encoding region of T. vaginalis virus (TVV). The in vitro transcripts of linearized pTVV-EGFP/NEO were electroporated into trophozoites and the transfectants transiently expressed EGFP after 16 h postincubation. Stable expression of EGFP was persistently detected by fluorescence microscopy and by RT-PCR in transfected trophozoites under G418 selection. Our study provides a novel and valuable approach for genetic study of T. vaginalis.