Multiblock poly(ether-ester) thermoplastic elastomers (PBT/PTMO) are based on sernicrystalline poly(butylene terephthalate) (PBT) and amorphous oxytetramethylene (PTMO) blocks. The copolymer was compounded with a filler content up to 10 wt% multi wall carbon nanotubes (MWCNTs) via a masterbatch process, which included milling, high shear mixing in the melt, and extrusion using a twin-srew extruder. From the compound several compositions of PBT/PTMO with 0.1-2.0 wt% of MWCNTs were prepared. Differential scanning calorimeter analysis showed that the fillers enhance initiation of recrystallisation, i.e. accelerate the nucleation of crystalline segments of PBT/PTMO. The morphology of the obtained nano-composites shows that MWCNTs are well dispersed in the matrix. Only some discrete nanotubes, apparently protruding from the matrix, could be distinguished on the fracture surface, still covered with a thin interphase matrix layer of PBT/ PTMO.