Conventional dry-jet wet fiber spinning techniques were used to fabricate continuous PAN/MWNT composite fibers with up to 20 wt.-% nanotube loading. PAN at the MWNT interface exhibited lower solubility under thermodynamically favorable conditions than in bulk PAN, indicating good interfacial interaction. Due to the PAN/MWNT interaction at the interface, thermal shrinkage decreases with increasing MWNT loading (5 to 20 wt.-%). For high MWNT loadings, PAN/MWNT composite fiber at 15 wt.-% MWNT loading showed an axial electrical conductivity of 1.24 S · m⁻¹. For all loadings, PAN/MWNT composite fibers exhibited higher tensile moduli than theoretically predicted by rule-of-mixture calculations, suggesting good reinforcement of the PAN by MWNT.