In this paper, the entropy generation rate in unsteady buoyancy-driven hydromagnetic couple stress fluid flow through a porous channel has been investigated. The partial differential equations are converted into their corresponding dimensionless equivalence, including the prescribed initial boundary conditions. These equations were solved using the Adomian decomposition method and the behaviour of some pertinent fluid variables, such as velocity, temperature, entropy generation rate and the irreversibility ratio were examined and discussed for different parameters of interest, which include, the Grashof number, the Hartmann's number, the Reynolds number, the Brinkman number and the couple stress pa- Graphs are shown to illustrate the findings.