The ability to effectively internationalize and the internationalization processes of firms have been the topic of widespread research efforts during the past 30 years. The purpose of this paper is thus to discuss internationalization theories from the point of view of the international business and entrepreneurship scholarship. It answers the two research questions: 1) what are the main theories’ weaknesses and strengths, and which model/models best fit small enterprises (SEs)’internationalization processes in the international business field? And 2) are there really different internationalization processes between the old and the new SEs, otherwise, the internationalization process in the international business field does it vary in the entrepreneurship field? If yes, which model can explain the new one? Research results show that the best model that fits SEs’ internationalization process in the international business field is the “Uppsala model” stated by Johanson and Vahlne, (1977) while an integration of the Uppsala model and the network model stated by Johanson and Mattson, (1988) bests explain the process of new SEs in the entrepreneurship field with taking into account the knowledge based theory as adapted in both cases. The paper concludes with plans for some future research and a call for international business and entrepreneurship scholars to produce more joint research.