The Timasius chinai species group is redefined and taxonomically revised. Twelve species are distributed on the Asian mainland from northeastern India to southeastern China and to the Malay Peninsula, on Tioman Island, and on Java. The two earlier described species, T. chinai (Lundblad, 1933) (from Indonesia: Java) and T. miyamotoi Andersen, 1981 (from Thailand and China; first record from Laos), are redescribed. Ten new species are described: Timasius anderseni sp.n. (from Vietnam), T. gracilis sp.n. (from China: Hong Kong), T. indicus sp.n. (from India: Meghalaya), T. laoticus sp.n. (from Laos), T. malayensis sp.n. (from West Malaysia), T. montanus sp.n. (from northern Thailand), T. schuhi sp.n. (from West Malaysia: Tioman Island), T. schwendingeri sp.n. (from northeastern Thailand), T. yangae sp.n. (from West Malaysia: Tioman Island and Selangor), and T. yunnanensis sp.n. (from China: Yunnan). Keys to the species are provided based on external characteristics and on the genitalia of the males.