A laboratory investigation of the geotechnical properties of a marine clay saturated with a series of monovalent, divalent, and trivalent cations revealed large differences in behavior which depend on the exchangeable cations. The exchangeable cations employed in this study are sodium (Na), potassium (K), ammonium (NH4), magnesium (Mg), calcium (Ca), and aluminum (Al) in order of increasing valency. An increase in the valency of the adsorbed cations leads to an improvement in the geotechnical properties of the marine clay, while for a constant valency an increase in the hydrated radius of the adsorbed cations results in a lower rate of consolidation. Analysis of the results show that geotechnical properties are improved for the marine clay with cations having higher valency and smaller hydrated ionic radius in the adsorbed complex. The beneficial changes in properties can be attributed to the improvement in the efficiency of flocculation as the valency of the adsorbed cations increases and the hydrated ionic radius decreases.