Environmental stimuli predictive of appetitive events can elicit Pavlovian approach responses that enhance an organism’s ability to track and secure natural rewards. We examined the activity of individual nucleus accumbens (NAc) neurons during the performance of approach behaviors. Animals were presented with conditioned stimuli that were either positive (the CS+) or negative (the CS-) predictors of reward. Approach responses directed at these cues were recorded as lever presses and were significantly more likely to occur during CS+ presentations. On the test day, 75% of NAc neurons exhibited changes in firing rate (termed 'phasically active') during CS+ presentations. Of these cells, 47% were characterized by time-locked increases in cell firing while 53% showed reductions in firing for the duration of the CS+. The same cells typically showed little or no change during CS- presentations. These results suggest that NAc neurons encode reward prediction and/or approach responses elicited by reward-paired cues.