Attentional habituation in response to emotional stimuli, an aspect of the interaction between cognitive and emotional processes that has received scant attention, was investigated. Event-related potentials were recorded using a 60-electrode array from 25 participants who attended to 120 presentations of three different picture types: emotionally negative (S−), positive (S+), and neutral (S0). The affective content of the stimulation was assessed, through questionnaires, by the participants themselves. N1 showed different patterns of habituation as a function of the stimulation: amplitudes indicated that S− was more resistant to habituation than S0 and S+. This pattern, which reflects a greater capacity of S− to attract and maintain the participant's attention, is interpreted as a manifestation of the “negativity bias,” a phenomenon that reflects an evolution-favored set of mechanisms that facilitate a rapid and intense response to aversive events.