Phytophthora rot of Angelica keiskei during the warm season is caused by Phytophthora nicotianae; however, few reports are available on which pathogen(s) cause the disease during the cool season. Therefore, 12 Phytophthora isolates that were obtained from diseased plants of Angelica keiskei in the Izu Islands, Japan from February to June of 2017 and 2018 were examined, analyzed taxonomically, and tested for pathogenicity. All isolates reproduced the original symptoms after inoculation of Angelica keiskei. In our phylogenetic tree based on cox1 sequences, these isolates formed a monophyletic clade with Phytophthora taxon parsley and Phytophthora sp. hybrid type 1. Five representative isolates were morphologically identical with Phytophthora sp. hybrid type 1 and caused the symptoms on onion. Based on these results, the isolates were identified as Phytophthora sp. hybrid type 1. This is the first report of Phytophthora rot of Angelica keiskei caused Phytophthora sp. hybrid type 1.