Polyamide6 (PA6)/acrylonitrile butadiene styrene copolymer (ABS) blends with unmodified multiwall carbon nanotubes (MWNTs) were prepared via melt-blending in a conical twin-screw micro-compounder with varying melt-mixing time. To improve the state of dispersion of MWNTs, non-covalent organic modifiers for MWNTs have been utilized: sodium salt of 6-amino hexanoic acid (Na-AHA) and 1-pyrene-carboxaldehyde (PyCHO). PA6/ABS blends with MWNTs have shown a phase morphology transition from ‘matrix-dispersed droplet’ type to ‘co-continuous’ type as a function of melt-mixing time with the exception of 40/60 PA6/ABS blend with PyCHO-modified MWNTs. Non-isothermal crystallization studies revealed the heterogeneous nucleating action of MWNTs through the presence of double crystallization exothermic peaks (at ∼192°C and >200°C) while pure PA6 shows bulk crystallization peak at ∼192°C. 40/60 and 60/40 (wt/wt) PA6/ABS blends with 5 wt% unmodified MWNTs exhibited electrical conductivity values of ∼3.9 × 10−11 S/cm and ∼4.36 × 10−6 S/cm, respectively. A significant enhancement in electrical conductivity was observed with Na-AHA and PyCHO-modified MWNTs (order of ∼10−6 and ∼10−4 S/cm, respectively). POLYM. ENG. SCI., 55:429–442, 2015. © 2014 Society of Plastics Engineers