This laboratory experiment was carried out to study the individual and combined effect of two organic acids (humic and oxalic acids) and salinity levels of irrigation water on the changes of chemical properties and the content of available phosphorus of two calcareous soils of Egypt. The soils were treated by either humic or oxalic acid at application rates of 0, 0.1, 0,2 and 0.4% and irrigated by one of irrigation water resources varied in their salinity levels at 100% of soil field capacity. The used three water resources were tap water (W1), sea water (W3) and mixed water between W1 and W3 with mixed ratio of 1:1 (W2). This experiment was carried out in plastic pots, where it arranged in completely block randomized system with three replicates. These pots were incubated at room temperature (25 ± 2 ^◦C)for 6 months. After that, soil pH, EC (dSm^-1), CEC (meq/100g), total and active CaCO₃ (%) and the content of available P (mg/kg) were determined. Organic acids applications resulted in a decrease of soil pH and its content of total CaCO₃ % and increased soil EC (dSm^-1), CEC (meq/100g), and the content of active CaCO₃ (%) and available P (mg/kg). On the other hand, increasing salinity levels of irrigation water resulted in a decrease of soil content of total CaCO₃ and increased soil pH, EC, CEC, active CaCO₃ and available P. The relative changes (RC, %) of the studied soil properties were varied widely from soil to anther depending on type and application rate of the used organic acids and salinity level of irrigation water.