Many tree species are planted on the Higashi-hiroshima Campus of Hiroshima University (Hiroshima Prefecture, SW Japan). Since 2020, multiple surveys have been conducted to clarify the flora here. We confirmed 6,535 trees belonging to 169 species. The annual carbon dioxide fixation rate of the representative trees identified in the study was 31.65 tons. We also identified Acer pycnanthum K. Koch (Sapindaceae), which is listed as a vulnerable species in Japan’s Red List. As tree species require a certain amount of space for growth, we consider sites such as school campuses useful for ex situ conservation and campus trees important for social amenities and carbon dioxide reduction.