Empirical studies have examined the effects of expertise and personality in group decision making. However, previous research has not examined these effects on influence and decision quality while using the group as the context for the individual. Consequently, two models were tested in which individual expertise affected influence on group decisions, with the relationship moderated by individual extraversion. In one model, this interaction is expected to be dependent on group extraversion, whereas in the other model the interaction is expected to be dependent upon group agreeableness. Three hundred and seventy six college undergraduates completed the Winter Survival decision-making task. The results were that expertise and extraversion were positively related to influence, but only in groups that achieved synergy. Moreover, the results showed that the effects of expertise and extraversion on influence were dependent upon group agreeableness, rather than group extraversion. Also, the interaction of influence and expertise predicted group decision quality. Results supported the importance of individual differences on group decision quality via influence. The results also support using a more nuanced approach to examine individual differences in groups rather than a group score such as a mean or standard deviation.