<p>This research focuses on the wrinkling instability of a tri-layer structure composed of a thin film, a graded interlayer and a homogeneous substrate. The composite structure is subjected to an in-plane uniform compression, and the lateral deflection of the film is assumed to be a harmonic function along the longitudinal axis. The shear modulus of the interlayer varies exponentially through the thickness direction. To determine the unknown constants of the Airy stress functions, the continuity conditions between the displacement and stress components are utilized at the interlayer interfaces. The minimization of the total strain energy stored in the film and the interlayer interface is employed for the wrinkling instability assessment. Finally, the variations of the critical wavelength, critical strain, wrinkling wave amplitude and stress components with respect to the stiffness ratio and thickness aspect ratio are investigated. The results of the current study indicate that both the critical strain and the wrinkling wavelength increase for a graded interlayer with a higher shear modulus compared to the substrate and/or the thin film. Furthermore, the wrinkling amplitude increases as the graded interlayer becomes softer than the thin film.</p>