Temperature effect has been investigated in this study on the phosphatases isolated from three algae representing different groups; a unicellular freshwater green alga Chlorella fusca, a filamentous green macroalga Cladophora glomerata and a filamentous freshwater blue green microalga, Phormidium faveolorum. The temperature dependence of the enzyme activity could be summarized as that 60 ºC was the optimum temperature for the enzyme activity in Cladophora glomerata as well as Chlorella fusca whereas Phormidium faveolorum had an optimum temperature of 70 ºC for both isolated enzyme fractions, the cell wall-bound and the secreted extracellular. The thermal behavior of the phosphatases isolated from the tested algae showed toleration to the thermal activation when p-nitrophenyl phosphate (pNPP) was utilized as a substrate which has been investigated to be itself is not sensitive to high temperatures. The two fractions of the enzyme isolated from the algae exhibited high stability at high temperatures even above 80 ºC