To understand the relationship between national diversity and conflict types (relationship and task conflict) in nationally diverse workgroups, we examined group members’ nationalistic attitudes regarding outgroup derogation (nationalistic derogation) and ingroup preference (national ingroup preference). A sample of 131 employees in nationally diverse workgroups was used to examine our hypotheses. A moderating effect of nationalistic derogation was found on the relationship between national diversity and both task and relationship conflict, such that national diversity was more likely to lead to both task conflict and relationship conflict when members had negative attitudes based on nationality toward the outgroup members. National ingroup preference was less influential on the relationship between diversity and conflict. Results are discussed for future research and practical implications.