As military organizations continue to evolve and become professionalized, women´s participation in the military is also increasing. The integration of women into armed forces and the relationship between unit cohesion and gender relations in military units, has been argued to have a negative impact on unit cohesion and military effectiveness. However, previous research on the subject has shown that gender differences in military units can have both positive and negative effects on unit cohesion. In light of this scientific controversy, the purpose of this paper is to determine whether heterogeneous groups in the military have a positive or negative impact on unit cohesion. Through an interview study, the case of the Swedish Armed Forces, it was found that heterogeneous groups tend to have a negative impact on social cohesion. Task cohesion on the other hand, was affected positively by heterogeneity and contributes favorably to teamwork in these military groups. The findings mentioned should, however, be evaluated in relation to the scope of the interview study constituting the responses of seven commanders, and the author´s interpretation of the empirical material that has emerged from this research.