This study examined the influence of extraversion’s two dimensions (i.e., dominance and sociability) on training performance and explored the effects of relevant intermediary factors (reward sensitivity, self-efficacy) on training motivation and outcomes. Using a sample of 251 trainees completing basic military training, findings revealed that dominance was positively associated with training motivation and with theoretical and practical aspects of training performance, whereas sociability was not. Moreover, responsiveness (a facet of reward sensitivity) mediated the relationship between extraversion and training motivation. Posttraining self-efficacy moderated the relationship between training motivation and practical performance such that training motivation predicted practical performance at moderate (but not high) levels of posttraining self-efficacy. These findings provide a fuller understanding of the relationships between several constructs that are highly relevant to training performance in similar contexts. The implications of these results are discussed, along with potential avenues for future research.