Antagonism towards diversity, an attitude reflecting low egalitarian ethical values, has been a topic within policing that has received increasing attention in the last decade. Using two-wave data and applying self-determination theory, we investigated how autonomy support versus autonomy frustration, ways of being motivated either through encouraging one's sense of volition, or otherwise, coercing and imposing pressures, can improve diversity attitudes through its relation with ethical values. Study 1 (n= 398 police officers and staff) found that autonomy-supportive communications fostered ethical values, and hence was negatively related to diversity antagonism. Study 2 (n= 859 police officers and staff) indicated that motivation to overcome prejudice mediates the relationship between ethical values and diversity antagonism. Perceptions of workplace culture as lacking in autonomy support acted as a boundary condition for the ethical values and diversity antagonism relationship; no relationship was present when autonomy support was low.