BACKGROUND: Lamotrigine has been shown to be effective in the long-term treatment and relapse prevention of depression in bipolar disorder. However, the neuropsychological mechanisms underlying these effects are unclear. We investigated the effects of lamotrigine on a battery of emotional processing tasks in healthy volunteers, previously shown to be sensitive to antidepressant drug action in similar experimental designs. METHODS: Healthy volunteers (n = 36) were randomized in a double-blind design to receive a single dose of placebo or 300 mg lamotrigine. Mood and subjective effects were monitored throughout the study period, and emotional processing was assessed using the Oxford Emotional Test Battery (ETB) 3 hours post-administration. RESULTS: Participants receiving lamotrigine showed increased accurate recall of positive versus negative self-descriptors, compared to those in the placebo group. There were no other significant effects on emotional processing in the ETB, and lamotrigine did not affect ratings of mood or subjective experience. CONCLUSIONS: Lamotrigine did not induce widespread changes in emotional processing. However, there was increased positive bias in emotional memory, similar to the effects of antidepressants reported in previous studies. Further work is needed to assess whether similar effects are seen in the clinical treatment of patients with bipolar disorder and the extent to which this is associated with its clinical action in relapse prevention.