In this work, the properties of polyester filaments with different cross-sectional shapes were investigated. Trilobal, flat and hollow shaped polyester filaments, having the same count, were produced by following the same route and production parameters. Properties, such as tensile strength, elongation, breaking load, unevenness etc., were investigated. Comparative evaluations of the test results with regard to the cross-sectional shapes were carried out. The results showed that cross-sectional shape of the filaments directly affected the yarn properties and trilobal filament containing polyester yarns showed better properties as compared to yarns containing filaments with a cross-sectional shape of hollow and flat.