Abstract The antiparasitic effect of peracetic acid (PAA) was evaluated against an infestation of the protozoan Trichodina spp . in naturally infected juvenile domestic seventh generation (F7) Striped Bass, Morone saxatilis . Replicated treatments (n=3) consisted of 1 and 2 mg/L PAA and a control; treatments were applied every other day for 3 treatments (30 min static exposure). Infestation intensity was enumerated 20 ‐ 24 h after each treatment by counting the number of Trichodina present in a wet mount of excised gill tissue. Neither treatment rate was able to completely eradicate the parasite, however 2 mg/L PAA resulted in a statistically significant reduction which equated to 75% reduction of observed parasites. The 2 mg/L PAA treatment regimen in the present study is proposed as a safe, environmentally friendly, and effective method for reducing the intensity of Trichodina infestations in Striped Bass.