Investigation the histopathological effects of (4s)-2-(4-hydroxy-3-methoxyphenyl) thiazolidine-4-carboxylic acid on intestine tissue of zebrafish were aimed. (4S)-2-(4-hydroxy-3-methoxyphenyl) thiazolidine-4-carboxylic acid is new synthesized substance which obtained from cysteine and valine. Because of thiazolidine derivates have important biological responses scientist work intensively on these compounds recent years. It is obvious that thiazolidine contained compounds will be used in future in the pharmaceutical industry to treat important diseases.After one week adaptation period zebrafish divided into four group (n=10) as one control and 3 experimental groups (0.2 mM,0.4mM 0.6mM). Intestine were dissected after 5 day of the exposure. Tissues were fixed with 10% neutral buffered formalin and dehydration were carried out in an ascending series of ethanol. Tissues were cleared in xylene, embedded in paraffin wax and cut into 5 µm sections on a microtome. The sections were stained with hematoxylin(H&E). Results were evaluated with light microscope. In control group normal intestine histology have been observed. In 0.2 mM degeneration and fusion at villi structures and inflammation at submucosa were detected. In 0.4 mM thiazolidine exposed group, degeneration and vacuolization at villi structure and hypertrophy at serosa were observed. In 0.6 mM thiazolidine exposed group, degeneration at vili structure, hypertrophy at muscularis externa, vacuolization at submucosa and increase in the number of goblet cells were observed.