The River Nile is the principal freshwater resource in Egypt, meeting nearly all demands for drinking water, irrigation, and industry. The objective of this present study is to characterize the current environmental variables and the existent populations of phytoplankton along a segment of the River Nile near Mansoura City. The direct estimation of phytoplankton cell number gave an estimation of the standing crop. A total of 214 different planktonic algal taxa belonging to 64 genera were identified.  Maximum peak of 106.9Х10⁶cellsl¹ was recorded at S2 in April, of which cyanophycean specieswere themostdominant. Most of used indices, especially those diatom-dependent ones, gave a reliable indication of water quality with distinct irregular local variations. A significant decrease in species diversity was recorded at S4 during June indicating a significant level of water pollution. However, the diversity index was 1.06 referring to a moderate to light pollution conditions. The saprobic index mean value is 1.96 indicating an oligosaprobic to β-mesosaprobic conditions and the existence of blue-greens indicates a degree of toxicity. The integrated results between (measured and calculated) generally described the Nile water quality as in moderated level with some cases of temporal disqualify of potable with poor to very poor status at some sites, which mean it is within the standard level of drinking water as approved by the national and international agencies. Although temporal and spatial data confirmed the importance to set some environmental legalization and policies to ensure that the Nile water is maintained appropriately for the identified usage sector.