The data on semi-aquatic turtles’ erythrocytes morphometric parameters still are not known, so the aims of this study were to determine the values of erythrocytes morphometric size and shape parameters and their differences between four pet turtle’s species. Blood samples of four turtle’s species: Trachemys scripta elegans (TSE ; n=5), Trachemys scripta scripta (TSS ; n=2), Graptemys pseudogeographica kohni (GPK ; n=2), Sternotherus odoratus (SO ; n=2) were taken from the dorsal coccygeal vein. Smears were stained according to the May-Gründwald Giemsa method. By using a computer assisted-image analyses system, morphometric measurements were performed (100 erythrocytes per smear) with the "SFORM" program. The size parameters of erythrocytes and erythrocytes nucleus (area, outline, convex area, minimal and maximal radius, length and breadth), as well as shape parameters for erythrocytes (ellipticity, elongation, solidity, roundness, form factor and contour index) were determined. In the TSS turtles significantly higher values of erythrocytes area, convex area, minimal and maximal radius and length were determined, respectively. Also, in the TSS turtles, significantly higher values of erythrocytes nucleus area, outline, convex area, minimal and maximal radius, length and breadth were found. According to the obtained data, we can conclude that the morphometric parameters of erythrocytes differ between turtle species, i.e. the TSS turtles have the largest erythrocytes with the largest nucleus. The findings in this study can be used as the baseline values in the assessment of health of the above species and also will be useful in future haematological studies related to these species.