Abstract: The present study describes the meristic, morphometric and Length Weight Relationship (LWR) of tropical silverside, Atherinomorus duodecimalis (Atheriniformes: Atherinidae) an important fishery in the Sea grass and mangrove habitat of Tinggi Island, Johor, Malaysia. A series of sampling survey was conducted in seagrass and mangrove habitats of Tinggi Island, using beach seine net. A total of 94 specimens (3.7-10.3 cm TL) used in this study. The results showed that meristic and morphometric features of the fish studied agreed well with a description of the holotype specimen MNHN A. 4382 and other silverside specimens. The only exception was observed in the upper jaw length and eye diameter as a percentage of head length. The allometric coefficient ‘b’ of the length weight relationship indicated negative allometric growth (b<3.0) in seagrass habitat and positive allometric growth (b>3.0) in mangrove habitat. To the best knowledge of the authors, this study presented the first reference on LWR for this species from Johor waters, Malaysia.