Nanolayer coextrusion is an innovative process allowing to create films composed of thousands of layers of alternating polymers with individual layer thicknesses below 100 nm [1]. It has been observed that below a certain layer thickness (around 10 nm for PS/PMMA nanolayered systems), the layers tend to lose their integrity, i.e. they break spontaneously during the process [2]. These layer break-ups were attributed to small interfacial fluctuations amplified by van der Waals forces [2]. To further investigate those instabilities at the interfaces, a model experiment was designed, consisting in studying the dewetting kinetics of a thin PS film embedded in between two thicker PMMA layers with no external force. It has been shown that the thin film dewetting kinetics can be modeled by balancing interfacial tension with viscous dissipation in the surrounding matrix. [3] In this study, we aim at investigating the effect of a shear flow on the dewetting kinetics using both experimental and numerical approaches. It constitutes a promising approach towards an understanding of the rupture phenomenon observed in the nanolayer coextrusion process. References. 1.M. Ponting, A. Hiltner, E. Baer Macromol. Symp. 2010, 294, 19 2.A. Bironeau, T. Salez, G. Miquelard-Garnier, C. Sollogoub, Macromolecules, 2017, 50, 4064 3.M.S. Chebil, J.D. McGraw, T. Salez, C. Sollogoub and G. Miquelard-Garnier, Soft matter 2018, 14 (30), 6256