The deformation mechanisms of a semicrystalline polymer (SCP) subjected to tensile loading were experimentally studied from nano to micro and macro length scales. The paper’s focus is on the development of anisotropic features at all scales during deformation. At the nanoscale, original results are presented based on in-situ SAXS (small-angle X-ray scattering) measurements. At the microscale, previously obtained results using in-situ ISLT (incoherent steady light transport) and postmortem SRXTM (synchrotron radiation X-ray tomographic microscopy) are briefly summarized. For all these techniques, original data treatments were carried out for quantifying the evolution of anisotropy in the material’s microstructure. At the macroscopic scale, a 3D digital image correlation technique was used for determining all the components of the Hencky strain tensor in the center of the necking region. New results are presented in this field for the studied SCP in terms of the quantity D = εL/|εT|: ratio of the longitudinal strain (along the drawing axis) to the transverse strain (perpendicular to the drawing axis). The main result of this study lies in a plot of variable D as a function of εL. This plot evidences the same three clearly distinct regimes as those obtained using SAXS, ISLT, and SRXTM experiments to measure anisotropy quantitatively at the microstructural level. This result proves that everything occurring at the microscale gives a signature at the macroscale and hence opens up new routes for the modeling of the mechanical behavior of such materials.