Nanofiltration membranes have proven their applicability in desalination as well as many other fields in water and wastewater industries. Two commercial nanofiltration membranes denoted as NF and ASP30 were chosen to be investigated in terms of their characteristics and performance in order to determine their suitability and applicability for brackish water desalination in Gaza Strip. In this work, membranes flux and rejection of two additional salts (Na2SO4 and KCl) is reported. Both membranes showed higher rejection rate for Na2SO4 (99% for NF and 75% for ASP30) when compared to KCl (36% for NF and 32% for ASP30). ASP30 had higher flux for both salts solutions (110 L.mˉ².hˉ¹ for Na2SO4 and 121 L.mˉ².hˉ¹ for KCl) while NF membrane had lower flux for both of them (78.4 L.mˉ².hˉ¹ for Na2SO4 and 72.5 L.mˉ².hˉ¹ for KCl). In addition, the variation of salt rejection versus permeation provides a possibility of optimizing operational conditions of both membranes. The results indicated good potential in applying both membranes to desalinate brackish water of Gaza Strip which is characterized by up to 2000 mg/l TDS of which Chloride is up to 700 mg/l.