Introduction: The biostimulant products are able to improve quality and quantity of medicinal plants. Objectives: The comparative effects of biostimulants foliar spraying on peppermint (Mentha piperita L.) were investigated. Methods: These studies were done on the basis of randomized complete blocks design in 3 replicates during 2015. Results: In field conditions, the highest leaves and stems dry weight by 400 mg/l chitosan (CH) + 400 mg/l citric acid (CA), essential oil content by 200 mg/l chitosan + 400 mg/l humic acid (HA) + 400 mg/l citric acid and menthol content in 200 mg/l chitosan + 800 mg/l humic acid + 400 mg/l citric acid were observed. In greenhouse conditions, the best results of those mentioned parameters were obtained by 400 mg/l chitosan + 800 mg/l humic acid + 400 mg/l citric acid, 800 mg/l humic acid and 400 mg/l chitosan + 400 mg/l humic acid + 400 mg/l citric acid, respectively. Conclusions: The foliar application of effective biostimulants could improve the yield quality and quantity of Mentha piperita.