This study was conducted to evaluate the ultrastructure and the scheme of cellular events occurring to cotton plant leaves after Tetranychus urticae infestation. Complementary information at the ultra-structural level were essential to provide further insight into the biological significance of the mite infestation. Data from the light and electron microscope examination of thin cross sections of cotton plant leaves under infestation with Tetranychus mites revealed different cytological modifications including mesophyll cell wall alteration, cytoplasm breakdown, and necrosis of cell and deformation which caused severe reductions in stomatal conductance & photosynthesis rate. Where, examination of light micrographs and ultrastructure thin cross sections of uninfested cotton plant (control) indicated the regular distributions of most cells and density in staining of most inter-cellular spaces and cell walls.