High quality BCF carpet yarns using polymeric filaments such as PA, PET and PP are manufactured by incorporation of heat setting operation into their production process. In this work the effect of heat setting time and temperature on various properties of Polypropylene BCF yarns was investigated. A total number of 17 Polypropylene BCF yarn packages were produced under identical spinning condition. The dry heat at temperatures 120, 130, 140 and 150 ?C was applied to 16 of samples for duration of 45, 60, 75 and 90 seconds. One of the packages was not heat treated. Carpet samples were produced from packages which had been heat set for 90 seconds at different temperatures. Results indicated that tensile strength, modulus, shrinkage % and bending rigidity decreased as heat setting time and temperature increased. It was found that while an increase in heat setting time and temperature caused work to rupture, crimp contraction% and yarn linear density to increase, yarn friction coefficient remained unchanged. The above phenomena led to production of Polypropylene BCF yarns with sufficiently stable twist set structure and low rigidity. Yarn uniformity is improved due to increase in stability of heat set yarn twist structure. It was found that heat setting operation causes individual filament components of the yarn to close up due to increase in crimp contraction, thus creating a better carpet surface. As far as pile compression% and pile height loss% are concerned, results show that a significant reduction in the above two parameters occurred as heat setting temperature increased. It was also found that pile resiliency was proportionally improved with an increase in heat setting temperature. This is due to the fact that the ratio of recovery% to compression% has increased. It was observed that temperature increase in 90 second heat setting time generally resulted in an increase in crystallinity percentage and decrease of crystal size while crystalline phase became more homogenous.It was observed that the crystalline stability of un-heat set yarn was less than all the heast set ones Thus it can be concluded that the quality of carpets woven using yarns with above specifications is enhanced by heat setting Polypropylene BCF yarns.