Acid treated modified montmorillonite clay was used as catalyst precursors for the synthesis of benzimidazoles through the room temperature stirring of aromatic aldehyde and o-phenylene- diamine. The modification of the clay was done by treating the clay with HCl to under controlled conditions to produce a porous matrix with high surface area. The modified clay was characterized by powder XRD, N2 adsorption-desorption and SEM-EDX analysis. The recyclability of the catalyst was also investigated and showed efficient catalytic activity for several catalytic run.