The study of emotions is an important area to consider within a workplace context, as the experience of emotions has been linked to employees' psychological outcomes and performance. This is especially important in a group context, as individuals working within a group can converge emotionally, producing a group affective tone. Models describing the emergence of group affective tone have generally ignored the role of group diversity. We develop a model which considers how the diversity of a group (in terms of personality) influences the development of groups' affective tone, through its impact on group identification, and also specify the impact of group affective tone on group performance. Practical applications of the model for a workplace context are discussed.