This meta-analysis of 260 independent samples assessed the effects of diversity training on 4 training outcomes over time and across characteristics of training context, design, and participants. Models from the training literature and psychological theory on diversity were used to generate theory-driven predictions. The results revealed an overall effect size (Hedges g) of .38 with the largest effect being for reactions to training and cognitive learning; smaller effects were found for behavioral and attitudinal/affective learning. Whereas the effects of diversity training on reactions and attitudinal/affective learning decayed over time, training effects on cognitive learning remained stable and even increased in some cases. While many of the diversity training programs fell short in demonstrating effectiveness on some training characteristics, our analysis does reveal that successful diversity training occurs. The positive effects of diversity training were greater when training was complemented by other diversity initiatives, targeted to both awareness and skills development, and conducted over a significant period of time. The proportion of women in a training group was associated with more favorable reactions to diversity training. Implications for policy and directions for future research on diversity training are discussed.