The purpose of this study was to investigate the effects of thyme oil (TO), chitosan nanoparticles (CS-NPs), and TO-loaded-CS-NPs on controlling Salmonella Typhimurium (S. Typhimurium) infection in broiler chickens when compared to ciprofloxacin (Cip) antibiotic treatment. The CS-NPs and TO-loaded-CS-NPs were initially characterized using a transmission electron microscope. Two hundred and forty broiler chicks were divided into six equal groups. Group 1 was given TO (1ml/4L of the drinking water). However, group 2 and group 3 were given CS-NPs and TO-loaded-CS-NPs in a 2 ml/chick dose by oral gavage. Group 4 was given a Cip (0.5 g/mL of drinking water). Treatments started on the 20th day of age and continued for 5 successive days. Each chicken in groups 1-5 was orally infected with 1 ml of 1 × 10