A label-free and reagentless immunosensor based on localized surface plasmon resonance (LSPR) sensing was developed for the detection of salbutamol (Sal). Silver triangular nanoparticles deposited on transparent indium tin oxide film glass were used as the sensing platform. The immunosensor was prepared by direct adsorption of antibody against Sal on the surface of silver triangular nanoparticles. LSPR bands were obtained by a basic UV-vis spectrophotometer in the transmission mode. The analytical performance of the biosensor for the detection of Sal was examined. Under the optimized conditions, a calibration plot for Sal was obtained with a linear range between 0.02 μg mL⁻¹ and 0.8 μg mL⁻¹ (r = 0.991). The detection limit was 0.01 μg mL⁻¹. The proposed biosensor has been used to detect the concentration of Sal in pig complex feed and pork liver samples. It is believed that the plasmonic immunosensor is simple, cost-effective and can be easily used for the detection of Sal in cases of its abuse in animal feed for field analysis.