In this present study, the effect of salinity and photoperiod on the growth of Nannochloropsis sp. and Tetraselmis sp. was examined to optimize microalgal growth. Different salinities (5, 10, 15 and 20‰) for Nannochloropsis sp. and (10, 15, 20 and 25‰) for Tetraselmis sp. were studied. Both microalgae were cultivated at two different photoperiod cycles (24:0 and 12:12 h light:dark). Maximum growth rates and cell concentrations for Nannochloropsis sp. and for Tetraselmis sp. were achieved at salinities of 10 and 15‰, respectively. In terms of photoperiod, the maximum growth rates and cell concentrations for both microalgae were obtained at photoperiod of 24:0 h light:dark. This study shows that the cell concentrations and growth rates of both microalgae are highly dependent on salinity and photoperiod.