The current study incorporates the composition-dispersion framework while integrating dark personality into group personality composition research. More specifically, we study the group level effects of Machiavellian composition in regards to group deviance. We provide a brief critique of the two most commonly used theoretical approaches to studying group personality composition and contend that the composition-dispersion approach, via polynomial regression and surface plotting, depicts a more complex and comprehensive set of relationships between group personality and group outcomes. Based upon prior research, we made hypotheses in line with both the supplementary (mean-level Machiavellianism) and complementary (level of dispersion) approaches to personality composition. Additionally, we hypothesized an effect of incongruence such that mean-level Machiavellianism and dispersion would jointly impact deviance. We found partial support for the supplementary approach, in that the group mean level of Machiavellianism was positively related to both interpersonal and organizational deviance. We did not find support for the complementary approach, in that dispersion level of Machiavellianism was not related to deviance. Using polynomial regression, we found further support that simple linear effects only explained part of the relationship between group Machiavellianism and deviance. Our findings elucidate the impact of incongruence on the Machiavellianism-deviance relationship within groups. We offer theoretical and practical implications to our findings.