In this manuscript, numerical and semianalytical solutions of electroosmotic flow of fractional Oldroyd‐B fluid through a vertical microchannel filled with a porous medium have been investigated. The fractional Cattaneo model is used to alter the energy equation. The Laplace and finite Fourier sine transforms have been used to get the semianalytical solutions as well as the finite difference method as a numerical solution. The results show that there is an excellent agreement between the two solutions. Moreover, the surge in velocity, flow rate, and heat transfer is extremely noticeable at the beginning of the time interval for various physical characteristics. Furthermore, as time passes, this phenomenon will reduce, and they will attain a steady state. Due to the existence of a different distribution of charges in the EDL at the channel walls, the velocity profile becomes asymmetric.