Organic matter is frequently encountered in both naturally occurring and engineered particulate media. Charged functional groups in the organic matter can lead to cation exchange within the clay interlayer, which results in the formation of an organic coating on the clay surfaces and alters the interfacial frictional regime in the soil mass. This study investigated the triaxial shear frictional behavior of montmorillonite particles coated with a controlled organic phase composed of quaternary ammonium cations. Through cation exchange, organic cations were loaded onto the clay’s interlayer exchange sites, with control on the density of organic coverage and structure of the organic cation. Results demonstrated that increasing the total organic carbon content of the clay resulted in increasing frictional resistance regardless of whether the increase in carbon content was attributable to increased density of organic loading, increased cation size, or increased cation tail length. Concentrating organic carbon in one of the quaternary ammonium cation branch positions led to measureable gains in strength compared with distributing the carbon over all four branch positions. Measured critical-state friction angles for the organoclays ranged between 34 and 61°, whereas all tested organoclays demonstrated peak strength coupled with contractive tendencies. The presence of the organic cations in the clay interlayer led to alteration of the structure within the interlayer and is believed to have combined with forces from electrostatic bonding between the organic cation head groups and the clay surface, as well as chain entanglement and dewatering, to contribute to the increased frictional resistance of the modified organoclays.