Performance apparel is playing a significant role in industry for special end use applications. One of the applications involves the formation of yarns to be made into performance fabrics through knitting or weaving. Performance CoolMax/Micro Modal, knitted fabrics, for purposes of this paper, are defined as fabrics used in specialty apparel, that are engineered for use in high-energy sports and activities performed in extreme environments. Clothing made of performance fabrics are said to be designed not only for fashion or just a passive cover for the skin, but to critically influence the comfort and performance of the wearer. Manufacturers have engineered these fabrics to manage moisture, regulate temperature, and provide protection from the surrounding environment. They are designed to interact with and modify the heat-regulating function of the skin as the surrounding environment interacts with them. In this study two different types of CoolMax/Micro Modal knitted fabrics (single jersey plated and interlock double face) with two various masses were produced for athletic sport suit. They were examined before and after sewing with two types of stitches (stitch type 512 and 601) and three different stitch densities. Tests were applied to determine the functional properties for performance depends on several factors like air permeability, water absorption and water absorbency to determine moisture management, abrasion resistance and crease recovery, which are quite important factors for knitted garments especially for sportswear. These properties may offer higher flexibility in designing such garments with optimized comfort properties. In addition to seam properties like seam thickness, seam stiffness, seam breaking force, seam pucker and seam appearance. All tests were carried out according to standards and took place into conditioned atmosphere of 21ºC and 65% RH. Comparisons have been made among them to determine the influence of knitted fabrics' structure on adequate stitch type and density for performance apparel.