In this study, ultrastructural changes in root tip cells and leaf cells of lentil plants treated with 4 different concentrations (0.25%, 0.5%, 1%, and 1.5%) of the herbicide fluazifop-p-butyl (FPB) were determined. The experiments were performed with light and transmission electron microscopy (TEM) and the chlorophyll content of the leaves was determined using spectrophotometric methods. The effect of FPB included alterations in cell walls, nuclei, plastids, cuticle, and epidermis. The obtained results indicate that the herbicide FPB has the ability to cause different kinds of abnormalities in various cell organelles, especially the cell walls in root tips. The effect of FPB was not limited only to the anatomy and plastid ultrastructure of the leaf, but the chlorophyll content was also affected.