Abstract This study aimed to assess growth performance of three strains of Nile tilapia (Chitralada 3, Uttaradit and Superblack) cultured in the salinity of 0, 5 and 15 ppt of rock salt water. The experiment was conducted between July 2015- November, duration of culture was 4 months. The 3x4 factorial (3 strains 4 salinity) in completely randomized design was used. Fish (average initial weight of Chitralada 3, Uttaradit and Superblack were 0.66±51.01 ,1.76±51.59and 0.25±50.14 g, respectively) were randomly stocked in each of 36 fiber glass tanks (600 L). Stocking density was 115 fish/m3, the fish were fed twice a day. All fish cultured in 25 ppt were died within 12 hours after experiment started. Results showed that the Average Daily Gain )ADG( of superblack strain(1.480±.14 g/day) was significantly higher than those of Uttaradit strain(1.190±.11 g/day) and Chitralada 3 strain (1.100±.47 g/day)) P<0.05). ADG of all three strains cultured in 5 ppt and 0 ppt were no significantly different )P>0.05). Feed Conversion Ratio (FCR) of Chitralada 3, Uttaradit and Superblack were 0.23±1.38 ,0.50±1.27and0.51±1.45 , respectively. FCR of three strains and three salinity levels were no significantly different )P>0.05). Survival rate of Chitralada 3, Uttaradit and Superblack were 70.77%70.53 ,% and 84.79%, respectively. Survival rate of three strains were no significantly different )P>0.05). Survival rate of fish cultured in 0, 5 and 15 ppt were 85.52%, 84.30% and 56.27%, respectively. Survival rate of fish cultured in 15 ppt was significantly lowest )P<0.05). There were no interaction between strain and salinity level )P>0.05).