The nature of work in contemporary organisations has become increasingly group orientated. Several studies have linked psychological collectivism with important outcomes for individuals working in groups. The present research sought to build upon existing research, via examining the performance benefits of psychological collectivism within the New Zealand context. This study had two main aims: to examine whether employees within New Zealand who are more collectivistic are better performing group members, and engage in increased taking charge behaviours; and to investigate the possible moderating role of TMX, or the quality of co-worker relationships, in these relationships. Participants in this study were employees from various businesses throughout New Zealand, representing a wide range of industries, who completed an online questionnaire. The questionnaire measured psychological collectivism, four dimensions of group member job performance (task performance, citizenship behaviour, counterproductive behaviour, and withdrawal behaviour), taking charge, and TMX-quality. To test the proposed hypotheses, correlation, regression, and moderation analyses were conducted in SPSS. Several of the proposed hypotheses received support: psychological collectivism positively predicted group member citizenship behaviour and taking charge behaviour, and negatively predicted group member counterproductive behaviour and group member withdrawal behaviour. TMX- quality significantly moderated the relationship between psychological collectivism and group member withdrawal behaviour. However, several of the proposed hypotheses did not receive support: psychological collectivism did not positively predict group member task performance, and TMX-quality did not significantly moderate the relationships between psychological collectivism and the other variables. Possible reasons why these hypotheses were unsupported are outlined. Additionally, significant non-hypothesized relationships were also obtained, which are discussed in detail. Concerning practical implications, organisations should aim to maximise psychological collectivism when necessary, via selection and placement or employee training and development programs. Moreover organisations should focus on improving the quality of co-worker relationships (i.e., TMX-quality). With respect to future research, research is needed which explicitly examines whether psychological collectivism can be developed in individuals. Taken together, the findings from this study highlight the far-reaching performance benefits of psychological collectivism and high-quality TMX in the workplace.