This paper investigates the non-modal linear stability analysis of rotating flow through porous media, governed by the Darcy–Brinkman fluid model with Coriolis force. A comprehensive understanding of instability in a rotating fluid-saturated porous layer is crucial for effectively controlling transport phenomena and optimizing the mixing process. A normal mode analysis is carried out, and the coupled Orr–Sommerfeld and Squire eigenvalue problem is developed to determine the maximum transient energy growth within a fixed time interval, allowing for the prediction of instability. By utilizing Singular Value Decomposition (SVD) to find the matrix exponential norm, we calculate the transient energy growth of the disturbances and determine the numerical range of our operator. By examining the numerical range and transient energy growth curves, we demonstrate that both rotation and porosity have a destabilizing effect on the flow. Across the entire range of porosities considered, the transient energy contours indicate that the porosity mechanism is a key factor in transient energy amplification, which reduces the critical Reynolds number. An unstable mode is detected at considerably lower Reynolds numbers, particularly at \( \text {Re} = 150 \) , \( \sigma = 0.25 \) , and \( \text {Ro} = 0.12 \) .