Adults of caligiform copepods are often found in plankton samples, in addition to the naupliar and copepodid stages. Here, we report on adult parasitic copepods of the families Caligidae and Pandaridae from plankton samples collected in Japanese and Chinese coastal waters. The following previously described species were found in 2008: Caligus calotomi Shiino, 1954; C. orientalis Gusev, 1951; C. undulatus Shen and Li, 1959; Lepeophtheirus semicossyphi Yamaguti, 1939; Metacaligus uruguayensis Thomsen, 1949, and Pandarus satyrus Dana, 1852 in Japanese waters; and C. orientalis and C. rotundigenitalis Yu, 1933 in Chinese waters. The findings of adults of Lepeophtheirus and Metacaligus in plankton samples represent the first such a record for each genus. Two new species of Caligus are also described from plankton taken in Japanese waters in 2008 and 2010. An ovigerous female collected from off Iheya Island, Ryukyu Islands, Okinawa Prefecture is described as Caligus quadrigenitalis sp. nov., and two adult females and a male collected from the Seto Inland Sea and off Hirado Island, Kyushu, western Japan is described as Caligus ogawai sp. nov.