Both sexes of a new species of Nitokra Boeck, 1865 were collected from a brown alga, Padina australis at Bangsaen sandy Beach in Chon Buri province, Thailand. Nitokra karanovici, sp. nov., is similar to many species of the genus in having a slender and cylindrical body shape, eight-segmented antennules in female and nine-segmented in male, exopod of female P5 with 5 setae; the new species shares the same armature formula of the swimming legs with the following six congeners: N. balli Rouch, 1972 from Long Island, Papua New Guinea; N. evergladensis Bruno, Reid & Perry, 2002 from Florida, U.S.A.; N. minor Willey, 1930 from Bermuda; N. minor mozambicae Wells, 1967 from Inhaca Island, Mozambique; N. platypus bakeri Chappuis, 1930 from the Philippines and Japan; and N. uenoi Miura, 1962 from Ryukyu Islands, Pacific. However, the new species can easily be distinguished from N. balli and N. uenoi by the number of setae on the female P5 Enp, and from N. evergladensis, N. minor and N. platypus bakeri by the much longer P1 Enp-1. Nitokra karanovici is most closely related to N. minor mozambicae, but it can be distinguished by the number of spinules on the anal operculum (6–7 in N. minor mozambicae and 11 in N. karanovici), and relative length of the P1 Enp-1 (slightly shorter in the new species). Therefore, we conclude that N. karanovici most resembles N. minor mozambicae as mentioned above.