The spinning of Poly Ethylene Terephthalate (PET) filament in laboratory-scale was studied. The objective was to study the effect of modified Calcium Carbonate (CC) with vinyltriethoxysilane (VTES) on the melt spinning of PET fibres. The CC was modified with VTES (2% v/v) in diethyl ether at room temperature for 24 h. The modification of CC with VTES improved agglomeration of CC, hydrophobic and heat resistance properties. These properties were expected that modified CC could be used as the filler in melt spinning of PET. The incorporation of modified CC in PET was spinnable. The addition of CC in PET improved its heat resistance. Also, the filler had an effect on the mechanical properties of polyester fibre.