One of the most important developments seen in the synthetic fibre industry is absolutely producing microfibres. Microfibres provide many distinguishing properties for different end uses. In this study, the effects of filament linear densities on the comfort related properties of polyester knitted fabrics were investigated. For this aim, microfilament polyester textured yarns of 110 dtex with 0.33 dtex, 0.57 dtex and 0.76 dtex filament linear densities and conventional polyester textured yarns of 110 dtex with 1.14 dtex and 3.05 dtex filament linear densities were knitted. Dynamic liquid moisture management, air permeability, water vapour permeability and thermal properties of the fabrics were tested. Consequently it is seen that fabrics with coarser filaments have a better capability of transferring liquid moisture. Lower air permeability results are observed with finer filaments, while there is no considerable difference among the samples for water vapour permeability. Also higher thermal resistance results are obtained for samples of coarser filaments.