Morphological characteristics of three gobiid Pseudogobius species (P. javanicus, P. sp. 1 and P. sp. 2) in their juvenile phases which collected in Sikao Creek, a mangrove estuary located in southern Thailand were described. Juveniles of them were distinguished from each other by the following characters: P. sp. 1 (n = 59, 7.4.13.3 mm SL) with two distinctive large blotches located on dorsal and ventral sides symmetrically of caudal fi n base; P. sp. 2 (n = 13,6.7.12.0 mm SL), with three blotches on caudal fi n base; and P. javanicus (n = 18, 6.5.11.8mm SL) with two distinctive large blotches on caudal fi n base in asymmetrical, upper one close to the lateral midline of body. All of these Pseudogobius individuals were collected within creek, mainly at middle reach, whereas no individuals from the marine area off the creek mouth, suggesting that these species spend most of their life within the estuarine habitat.