The fowl tick, Argas persicus (Oken), is of veterinary importance as a parasite of poultry and wild birds.The antitick efficacy, in vitro and in vivo, of peracetic acid (PAA) and deltamethrin (DMT) was tested separately against A. persicus through the dipping technique. PAA (0.5 %) was highly efficient against soft tick larvae (A.persicus), resulting in 100 % mortality after 2 min. The lethal concentrations LC50 and LC95 were 0.310 and 0.503 %, respectively. The lethal time values LT50 and LT95 were 5.34 and 40.00 min, respectively, after treatment with PAA (0.25 %). Two minutes after exposure to DMT, LC50 and LC95 values were 0.033 and 0.052 % (33.204 and 51.527 mg/L), respectively. The LT50 and LT95 values were 27.03 and 305.46 min, respectively, after treatment with 0.025 % DMT (25 mg/L). After dipping in PAA (0.5 %), the chickens did not show respiratory signs or inflammation on the eyes and/or skin. By contrast, temporary coughing, sneezing, and ocular inflammations without dermatitis were observed in chickens dipped in DMT (0.05 % or 50 mg /L). Seven days posttreatment (PT), the reduction in the percentages of A. persicus infesting laying hens were 99.15 and 63.42 % after dipping in PAA and DMT, respectively. However, complete elimination of the number of ticks occurred after 28 days PT with DMT. PAA inhibits molting effectively (28 %) when compared with that of DMT (52 %). Results indicated that PAA is a more potent and promising acaricide against A. persicus (in vitro and in vivo) than DMT.