The present work shows the numerical analysis to study the free vibration characteristics of a sandwich panel in which graphene reinforced polymer composite is used as the face sheet and titanium as a homogeneous core exposed to non-uniform temperature variation. As these sandwich panels are exposed to different environmental conditions during their service, the vibration resposne of sandwich panel under thermal environment is studied. The finite element approach is utilized to study the influence of different graphene grading patterns, temperature-dependent properties, and non-uniform temperature variation on the buckling and dynamic behavior of the sandwich panel. The temperature-dependent material property of the non-linear type is considered. The temperature distribution at 95 % of buckling temperature affects the dynamic behavior significantly regardless of the graphene grading patterns. The uniform temperature field and the model heated in the middle of the panel influences vibrational behavior efficiently compared to the camel hump temperature field and heated at an edge of the plate. Further FG-X has higher natural frequencies compared to FG-UD and FG-O grading patterns. Several other obtained responses are discussed in this paper.