Emerging evidence suggests that dopaminergic and serotonergic functioning are altered in pathological gamblers; yet, there are no FDA-approved medications for pathological gambling and there have only been a limited number of clinical trials that have been conducted. Olanzapine was identified as a candidate medication for pathological gamblers because it modifies both dopaminergic and serotonergic function. Moreover, preliminary studies have shown that olanzapine effectively reduces impulsivity in other psychiatric disorders, a pharmacological target of interest for pathological gamblers. In this study, 21 pathological gamblers, whose primary gambling activity was video poker, were enrolled in a seven-week, double-blind, placebo-controlled trial. Outcome measures included self-reported urges for gambling, frequency of gambling behavior, and self-reported mood and anxiety levels. The results revealed that all study participants reported reduced levels of gambling urges, gambling behavior, and mood and anxiety symptoms. Olanzapine administration was not associated with an incremental effect versus placebo. While these findings suggest that olanzapine is not an efficacious treatment for video poker pathological gamblers, olanzapine may still be an effective treatment for a specific subset of pathological gamblers, including those with a co-occurring psychiatric disorder.