The effectiveness of lactoferrin against Potato virus x (PVX) in vitro and in vivo have been evaluated. Four concentrations of lactoferrin 100, 250, 500 and 1000 mg/L were examined either in vitro culture medium or in vivo (greenhouse). The presence of the virus was evaluated by ELISA technique. Results demonstrated that application of 1000 mg/L lactoferrin by spraying or combined with tissue culture proved to be an effective method for PVX-inhibition as compared with other concentrations. Also, results of antiviral activity of lactoferrin at concentration 1000 mg/L showed great potential as phytotherapeutic source to produce quality and health plantlets for rapid and large scale in vitro production.