Much research has pointed to the effectiveness of cognitive dissonance treatments in promoting pro-environmental behaviour and suggested that information-based treatments may have limited effectiveness. The current study sought to examine the impact of arousing cognitive dissonance in relation to the issue of plastic pollution in a between-group experiment, with participants (N = 24) randomly assigned to either a dissonance or information-only condition. Participants’ psychophysiological responses to ocean plastic pollution stimuli were measured via Galvanic Skin Response and Electroencephalography, while self-report questionnaires measured participants’ feelings relating to the issue and intention to reduce their plastic waste, having viewed the stimuli. No significant differences were found between the dissonance and information-only conditions on any of the measures. However, due to the methods used and the limitations of this study, further research is recommended to ascertain the impact of incorporating dissonance-arousing techniques into messaging aimed at encouraging people to reduce their plastic waste.