The influence of poly (vinyl) pyrrolidone (PVP) adsorption on the zeta potential and water loss of raw Saudi bentonite (B) and Na-rich Saudi bentonite (Na-B) suspensions was investigated. Phase analysis of raw Saudi bentonite was characterized by XRD, and chemical analysis was investigated by XRF. Adsorption study was performed by patch technique. The zeta potential and water loss of B and Na-B suspensions were measured at different PVP concentrations. PVP adsorption on B was fitted by Freundlich model. For Na-B, the adsorption isotherm closely fitted the Langmuir model and showed a higher affinity and greater adsorbed amount of PVP than B. Before addition of PVP the zeta potentials of B and Na-B suspensions were −30 and −41 mV, respectively. In presence of PVP the zeta potential of raw bentonite suspension decreased, then increased with increasing PVP concentration; the reverse trend was observed in the case of Na-B suspension. The presence of PVP greatly influenced the water loss of B dispersion but had a slight effect in the case of Na-B.