Yarn hairiness is one of important yarn parameters, which is used for yarn production quality control. It is usually characterized by the amount of free fibres (fibre loops, fibre ends) protruding from the compact body of yarn towards the outer yarn surface. Yarn hairiness is important because has great influence on the weaving process and parameters of textile product (porosity, permeability, transport of moisture, comfort, aesthetic properties and hand mainly). The main factors influencing hairiness are: type of fibres, yarn twist, yarn count, blending ratio and yarn production technology. The main aim of this article is determination of dependencies between cotton fiber parameters, yarn construction and yarn hairiness. It is found that yarn hairiness is critically dependent on the yarn fineness. Coarse fibres have higher hairiness. The influence of twist is not so high but in agreement with empirical findings the higher twist leads to the lower hairiness. The influence of fibers parameters is not important. The UHM only show some influence on hairiness.