Background: Trichomonas vaginalis (TV) parasitic protozoan is a widespread sexually transmitted infection. It is emphasized by the World Health Organization that the global prevalence of TV is rising. The parasite causes infections in the urogenital system in humans, and recently it was determined that it has a potential effect on both prostate and cervical cancer. Due to its being a significant public health problem, new treatment methods need to be developed to combat the parasite. Objective: Previous studies on the use of stabilized hypochlorous acid (HOCl) indicated that it has a potential microbicidal effect on different types of microorganisms. From this point, we investigated the effect of stabilized HOCl on TV in vitro. Material and Methods: Direct microscopy for time-kill (TK) assay, and vital trypan blue assay were performed to determinate the effective dose (1/2 to 1/64 dilution) and time (0 to 90 min) of stabilized HOCl action on live TV. For negative controls, sterile PBS alone was added to TV and medium. Results: The death of TV was dose and time dependent. Parasites were killed at a dilution of 1/2 and 1/4 at 0 min and for the rest of the time courses at these dilutions. Whereas, decreased effect was observed on TV viability with dilutions of 1/8,1/16 and 1/32 with different time courses and there was no effect at a dilution of 1/64. Conclusions: According to our findings, stabilized HOCl has an effect on TV viability and this is the first study on the effect of HOCl on TV.