The Length-Weight Relationship (LWR) and condition factors (CF) of 10441 the oriental river prawn Macrobrachium nipponense collected from Anzali lagoon from March to December 2015 were studied. Length, weight and other external features of all specimens were measured. The Total length and body weight of M. nipponense ranged from 12.3-97 mm and 0.1-11.7 g respectively. A strong positive relationship was observed between the shrimp length and weight in both sexes (r= 0.95). There were significant differences in the condition factors of males and females (p < 0.05). The lowest CF value was observed in station 1 (CF= 1.28 ± 0.04) and the highest in station 2 (CF= 1.38 ± 0.34). In this study the regression coefficient (b) was lower than 3.0 for females and 3 for males, and combined sexes which was reflecting allometric growth of the M. nipponense.