In this study, the authors investigated the relationship between work team effectiveness and two distinct aspects of the personality composition of teams: (a) the average level of a given trait within a team, referred to as team personality elevation (TPE); and (b) the variability or differences in personality traits found within a team, or team personality diversity (TPD). Retail assistants (N= 328) working in 82 teams were assessed on a broad range of traits organized around the framework of the Big Five personality factors. Across the set of Big Five traits, TPE and TPD predicted unique variance in ratings of team job performance. For each specific trait of the Big Five, either TPE or TPD predicted team performance. For the traits of conscientiousness, agreeableness, and openness to experience, TPE was positively related to team performance; TPD of extraversion and emotional stability was positively related to team performance.