The cooperation process has hardly been studied in multicultural organisations. Empirical and theoretical studies have identified its functioning process by its nature or by its stimulating factors; however there is a lack of research concerning the interpersonal cooperation process in intercultural organisations. This research paper proposes an interpersonal cooperation model elaborated firstly in a mono-cultural working environment, which is then applied to an intercultural organisation in order to elaborate a cross-cultural model for cooperation. The model suggests that interpersonal cooperation is a dual process and based on a political dimension (a calculation process of individuals which can prevent cooperation) and identification dimension. Based on an empirical research method, the paper presents the application of the model through an inter-site case study including 30 interviews in an international company amongst 10 different nationalities. Moreover, the case study stresses that the political dimension of the model is not relevant in an intercultural context because the identification dimension prevails. The identification process reflects a strong organisational culture of the company Prometheus which has a human resource management focus on a common understanding of others where the national cultural differences become secondary (based on an anthropological conception of human beings). Finally, the theoretical implications of the study argue that interpersonal cooperation process is not the same in mono-cultural and intercultural organisations. It can also be concluded that managers should build a strong organisational culture in intercultural organisations and multiply common interpersonal projects in order to create a strong feeling of belonging to a work group and to a company.