Attenuated total reflection (ATR) properties, scattered light and emission due to surface plasmon (SP) excitation from merocyanine (MC) Langmuir-Blodgett (LB) films on Ag thin films were investigated. A Kretschmann configuration of the ATR measurement, prism/Ag thin film/air or prism/Ag thin film/MC LB film/air structure, were used for the SP excitation. The thicknesses and the dielectric constants of the Ag thin films and the MC LB films were obtained from the ATR measurement. Scattered light due to the SP excitation was also observed from the Ag thin film or the MC LB film in the ATR measurements. Furthermore, emission was observed through the prism when a laser beam was irradiated to the sample from the air. The angles of the emission peaks almost corresponded to the resonant angles of the ATR curves. It was considered that the emission was due to the SP excitation and depended on the surface roughness of the films. The intensity of the emission from the Ag thin film strongly depended on the incident angle of the laser beam.