This study investigates crossmodal fear generalization, testing whether conditioned fear spreads between different sensory modalities. Participants in the unimodal group were presented with visual stimuli--images of a sparrow (CS+) and a laptop (CS-)--while the crossmodal group received auditory stimuli--sparrow calls (CS+) and keyboard typing sounds (CS-). During the generalization phase, both groups were presented with conceptually similar visual stimuli (GSs) with varying similarity to the CS+ (e.g. high: Pigeon, moderate: Duck, low: Goat). Measures included US expectancy ratings, skin conductance responses (SCR), and functional near-infrared spectroscopy (fNIRS). Results showed successful fear acquisition in both groups, with significantly higher US expectancy ratings, SCR, and mPFC HbO activity for CS+ compared to CS-. Both groups exhibited a gradient effect during the generalization phase, with GSs that were more perceptually similar to the CS+ eliciting higher US expectancy ratings. These findings support crossmodal fear generalization and offer new insights into the overgeneralization of fear in anxiety disorders.