Possible allosteric inhibitors of MPro were investigated using in silico methods. To this end, FDA-approved drugs in the DrugBank database were subjected to a virtual screening, and drugs that strongly bind distant from the catalytic site of MPro were identified using molecular docking. Among the identified drugs, Dihydroergotamine (DHE) was chosen for further investigation due to its highest binding score against MPro in the molecular docking experiment. The allosteric inhibition potential of DHE toward MPro was demonstrated by applying some computational tools on the trajectory files which were obtained from the Molecular Dynamics Simulations. Results support that the hydrogen bonding interactions of DHE with GLU278 and THR280, located between Protomer A and Protomer B, affect the structure of the side chain of CYS145 at the catalytic site of MPro. Considering the role of CYS145 in the catalytic cycle, this structural change is likely to be a mechanism for inhibiting MPro.