This paper explores the Japanese concern with Cambodian Buddhism from the 1930s to 1950s. In 1934, a Buddhist magazine entitled Kaigai Bukkyo Jijo[Situation of Buddhism Overseas] was launched. From the beginning, this magazine was overly focused on the Angkor monuments. In the early 1940s when the Japanese army was stationed in Cambodia, a Buddhist sect sent delegates, and Japanese ethnologists carried out fieldwork, but they paid scant attention to modern aspects of Cambodian Buddhism. While a few Japanese scholars recorded accounts of modern Buddhist institutions in the intervening years, the perception of Cambodian Buddhism as “ancient” persisted until the early 1950s when Japanese monks and scholars became involved in Asia again through the World Fellowship of Buddhists. The second World Fellowship of Buddhists conference held in Tokyo became the first opportunity for Cambodian monks to visit Japan. Venerable Huot Tath who had spearheaded the modern reform of his sect from the early 20th century participated in the second conference in 1952, along with his close supporter and reformist collaborator Suzanne Karpelès, the ex-secretary general of the Cambodian Buddhist Institute. Thus, it was not until the 1950s that Japanese Buddhist monks and scholars sincerely faced contemporary Cambodian Buddhism, and provided an opportunity for the main protagonists of pre-war Buddhist reformism in Phnom Penh to achieve a reunion.