Because the classical 3D crystal growth is frustrated, crystallization under confinement can lead to unique crystal morphologies and orientations. Such unique features can eventually lead to enanched propreties, like gas barrier properties1. The nanolayer coextrusion is a novel and innovative process that allows, through layer multiplying elements, combining two polymers in a layered structure, creating nanolayered films with continuous and regular layers down to 10 nm thick. It appears to be a relevant tool to study the structure–property relationships of confined polymer crystallization2 and to determine the critical factors that control the confined structures. In this work, PLLA was confined by poly(styrene) (PS) and polycarbonate (PC) using nanolayer coextrusion. Ten multiplying elements (2049 layers) were used in order to reach 20 nm continuous layers of PLLA, confined between slightly thicker PS or PC layers (around 60 nm) in final 100 μm thick films. Those films can be studied as extruded and after a subsequent annealing at different temperatures above the glass transition temperature of PLLA but below the glass transition temperature of the confining polymer, in order to maintain the layered structure. The effect of the confinement and of the annealing has been investigated on the crystallization morphologies and orientations, using mainly X Ray diffraction.