This study reports the Length-weights relationships, and relative weights of 5 demersal fish species of Persian Gulf. Specimens were caught during fishing surveys using different types of fishing gears between April 2008 to December 2010. A total of 653 individuals were sampled. The parameter b ranged between 2.626 (Acanthopagrus latus (Houttuyn, 1782)) to 2.995 (Carangoides talamparoides (Bleeker, 1852)). The coefficient of determination (r2) was very significant for all the species. Relative weight differed significantly (Kruskal-Wallis test, P< 0.001) with best performance by Saurida tumbil (Bloch, 1975) and Nemipterus japonicus (Bloch, 1791). Otolithes ruber (Bloch and Schneider, 1801) showed 90% mean weight calculated for this species. To the authors’ knowledge, the length-weight relationships and the Relative weights presented for N. japonicus, C. talamparoides and S. tumbil are reported for the first time from the Persian Gulf, but A. latus and O. ruber have not been previously reported for the Iranian water fishes.