The objective of this work is to investigate the rheological performance of a locally-sourced bentonite from Sabah for use as drilling fluid against a commercial benonite from India. The rheological properties of the drilling fluids were obtained by using standard testing apparatus such as mud balance, viscometer and filter press. It was observed that the Sabah bentonite has lower values of density, gel strength (GS), plastic viscosity (PV), yield point (YP) and filtration loss as compared to the Indian bentonite. The Malaysian bentonite did not meet the API required viscometer reading of 600 rpm. However it was found that by adding 1.0 ppb of NaOH as an additive to the mud, the rheological performances of the mud improves significantly to meet the API standard. Economic analysis indicates that the treated Sabah bentonite mud is much cheaper than the Indian bentonite by as much as 61%. The results of this work showed that the locally-sourced treated bentonite is technically and economically feasible for use as drilling fluid application.