The role of feeding method, as an important parameter in competition with thermodynamic parameters, on determining the nanoclay partitioning and its impact on microfibril formation in PP/PBT blend nanocomposite fibers were investigated. In the direct feeding method in which all components were fed into the extruder simultaneously, the major part of nanoclay with almost unchanged interlayer d-spacing was located in the PP matrix and the rest of the nanoclay partitioned into the PBT dispersed phase. However in the PBT based master-batch method nanoclay, due to much greater melt intercalation occurred, remained in PBT droplets in the form of tactoids and/or platelets. In the masterbatch feeding method, incorporation of compatibilizer assisted more fraction tactiods and/or platelets to be transferred from PBT to the PP matrix while in the direct method it enhanced the extent of melt intercalation in the PP matrix. It was demonstrated that the nanoclay concentration in PBT droplets plays an important role in the extent of the microfibril formation during the melt spinning process. While at low organoclay loading (1 wt%) fine microfibrils could be formed in the fibers prepared by both methods of feeding, at higher organoclay loading (3,5 wt%) uniform microfibrils could hardly be developed in the fibers,particularly, in the masterbatch feeding method due to high melt elasticity of the PBT droplets and uneven dis-. tribution of platelets and/or tactoids in the droplets.