The effects of biostimulants on raspberry remain insufficiently understood, particularly in relation to cultivar-specific responses and the potential of remote sensing for treatment evaluation. The aim of this study was to assess the impact of foliar-applied biostimulants on yield and physiological responses of two floricane raspberry cultivars, Glen Ample and Przehyba, using UAV-based multispectral imaging under field conditions. Five treatment variants were tested, including a control and four biostimulant formulations based on animal-derived amino acids, plant-derived amino acids, seaweed extract, and seaweed extract combined with animal-derived amino acids. Biostimulant application significantly affected yield and fruit number per plant, whereas fruit weight remained unchanged. The highest yield values per plant regardless of cultivar were associated with treatments based on plant-derived amino acids (2578.78 g) and seaweed-containing (2483.36–2544.49 g) formulations, while the lowest values were recorded in the control (2335.66 g) and after the application of animal-derived amino acids (2351.80 g). Multispectral analysis revealed treatment-dependent temporal changes in vegetation indices, with clearer trends emerging after aggregation of relative percentage changes across measurement intervals. These results indicate that biostimulant effectiveness in floricane raspberry is strongly dependent on cultivar, formulation type, and temporal context. UAV-based multispectral imaging proved to be a promising non-destructive tool for tracking physiological responses to biostimulation under field conditions