The present study rigorously tests whether an arbitrary stimulus that signals threat affects attentional selection and perception. Thirty-four volunteers completed a spatial-emotional cueing paradigm to examine how perceptual sensitivity (d′) and response times (RTs) were affected by a threatening stimulus. On each side of fixation, 2 colored circles were presented as cues, followed by 2 Gabor patches, 1 of which was tilted and served as target. The color of 1 of the cues was paired with an electric shock, while others remained neutral. The target could be presented at the location of the threat-associated cue (Valid), at the opposite side (Invalid), or following neutral cues. Stimulus onset asynchrony (SOA) between cue and target was either 100 ms or 1,000 ms. Results showed increased perceptual sensitivity (d′) and faster RTs for targets appearing at the Valid location relative to the Invalidly cued location, suggesting that immediately after cue presentation, attention was captured by the threat-associated cue. Crucially, following this initial exogenous capture, there was also enhanced perceptual sensitivity at the long SOA, suggesting that attention lingered volitionally at the location that previously contained the threat-associated stimulus. The current results show an effect of threatening stimuli on perceptual sensitivity, providing unequivocal evidence that threatening stimuli modulate the efficacy of sensory processing.