Emotional states are known to influence how people process relevant information. Here, we address the impact of emotional state on irrelevant information. In this experiment, participants were randomly assigned to a neutral or positive mood induction, and then completed a task that involved viewing a sequence of overlapping pictures and words. They were instructed to attend to the pictures and ignore the distracting words. Following a filled interval, implicit memory for the distracting words was tested using a word fragment completion task. Individuals in the positive mood group showed increased implicit memory for previously irrelevant information compared to those in the neutral mood group. These findings are consistent with the view that positive mood broadens attention to include encoding of irrelevant information in the environment, and this can impact subsequent performance.