The paper aims to explore a role of the concept of “constitutionalism“ in the recent constitutional debates concerning the re‐interpretation and amendment of the Constitution of Japan (particularly Article 9 which has been cherished as a ‘pacifism‘ clause by the Japanese people since itspromulgation) by shedding light on two intertwining elements of constitutionalism: one works as a safeguard against change and the other as a driving force to change. The paper also examines how far the concept of constitutionalism takes hold in Japan under the international influences, particularly focusing on two periods such as one just after World War II and the other after the end of the Cold War.The word “rikken‐shugi“ (constitutionalism) has attracted attention beyond academics in the recent constitutional debate on Article 9 of the Constitution of Japan. In 2014 Japanese government changed the interpretation of Article 9 and realised the legislation based on the new interpretation in 2015, which allows Japan for the first time to use a right of collective self‐defence under certain limited conditions. Many constitutional legal scholars have criticised the change of the interpretation (and the legislation as an outcome) by claiming that they were against “constitutionalism“. On the other hand, some international legal scholars have legitimatised the government‘s position (“positive pacifism“) by emphasising the importance of enabling Japan to play a more active role in maintaining world peace, which they argue is encouraged by the constitution itself. Furthermore, taken into account the fact that the Liberal Democratic Party (LDP) for the first time manages to attain a two‐third majority at both Houses of the Diet (one of the conditions for the constitutional amendment), the LDP is presently eager to push forward the amendment process including amendment of Article 9 despite the fact that there is no urgency to amend the constitution as the LDP government chose an easier route as re‐interpretation of Article 9 rather than a tougher one as constitutional amendment in order to pass the above crucial legislation in the Diet. It is also interesting to note that the present LDP pre‐proposal refrains from repeating the previous LDP constitutional amendment proposal in 2012 which showed a rather sceptical attitude toward Western constitutionalism (the 2012 proposal criticized the bill of rights in the present constitution as an import of Western thoughts and argued the necessity to bring back traditional values of Japanese society). Therefore, it is useful to analyse the usage of constitutionalism in the Japanese context from a wider perspective of global constitutionalism.