The Asian longhorned beetle, Anoplophora glabripennis（Motschulsky）（Coleoptera: Cerambycidae）, is a highly invasive species worldwide. Recently, its invasion has been detected in multiple locations across Japan. For the development of an effective and efficient control protocol, we urgently need to understand the ecology of A. glabripennis in Japan. Therefore, this study investigated the seasonal prevalence of A. glabripennis in an urban area of Tsukuba City, Ibaraki Prefecture, Eastern Japan. We regularly searched 27 maple, lacebark elm, or katsura trees for A. glabripennis adults from late May to mid-September or early October in 2022 and 2023, resulting in the collection of 172 individuals. Notably, ＞80% of the individuals were collected between late June and late July in both years. The sex ratio was not biased toward males or females, and their occurrence period coincided. These findings highlight the importance of implementing control measures for A. glabripennis adults, such as insecticide spraying and direct catching, during the late June to late July period in Ibaraki and possibly southward regions of Japan.