The adsorption of the tri-ethylene glycol mono-n-decyl ether (C₁₀E₃) nonionic surfactant, characterized by its self-assembled lamellar phase above the critical micelle concentration (cmc), in a wide range of concentration, onto a layered clay mineral (montmorillonite) has been studied. C₁₀E₃ exhibits a high affinity for the montmorillonite (Mt) surface with an adsorption isotherm that differs strictly from previous studies on the adsorption of nonionic surfactants onto clay minerals for which a maximum of adsorption was reached below cmc. The self-organization in a lamellar phase changes the interaction potential between C₁₀E₃ and Mt, a surface that favors the aggregation of normal bilayers which expands the interlayer space at wide values (>40 Å) while keeping the exchangeable Na⁺ cations conferring dual hydrophilic–hydrophobic behavior for the hybrid layered materials. Depending on the C₁₀E₃ phase state (in monomers or in a lamellar phase), the adsorption leads to four distinct surfactant arrangements (lateral layers to normal tilted bilayers) within the interlayer space of Mt. The hybrid layered materials show a thermal stability at 350 °C with a collapse of their interlayer space at 13 Å due to the degradation of the hydrocarbon chains of C₁₀E₃. FTIR during thermogravimetry analysis permits the identification of the portions of C₁₀E₃ corresponding to ethylene oxide groups in close interaction with the Mt surface.