The crystallization behavior and the crystalline structure of nylon6-clay nanocomposites are investigated with regard to the processing conditions and thermal treatment. Microextruded bulk samples as well as blown films are under concern. The often reported nucleating effect of the clay particles is shown to strongly depend on the processing parameters prior to the solidification step, namely, the shear intensity which promotes self-nucleation and the temperature of the melt which regulates the density of these unstable nuclei. The MMT content influences the crystallization kinetics and the crystalline structure via the shear amplification phenomenon which increases the densities of both the shear-induced and the MMT-induced nuclei. The MMT platelets also turned out to hinder the crystal growth. The cooling rate plays a major role on the final crystalline structure by shifting the crystallization temperature in the specific growth range of either the alpha- or the gamma-crystal forms of the nylon6 matrix. Blown films corroborate the findings from microextruded samples regarding the competition between nucleation and growth in the resulting crystalline form of the nylon6 matrix. Besides, the strong texturing of the nanocomposite films provides information on the local arrangement of the chains and crystal unit cell on the MMT platelets.