Intercalation products based on ionic exchange reaction between cationic dye methylene blue and Na+-montmorillonite were prepared. Montmorillonite particles intercalated with methylene blue were characterized using X-ray diffraction, infrared spectroscopy, elemental and thermo-gravimetric analysis. The results showed that intercalation of dye molecules within the interlayer spaces of montmorillonite has successfully occurred and a degree of layers coverage equal to 81 % of cationic exchange capacity was achieved. The obtained coverage results in an increase of 5.8 Å in the basal spacing of silicate layers compared to pure montmorillonite. XRD results also indicated that the intercalation process was only dependant on intercalant concentration. Other factors such as time of the process and clay concentration had no effect on the obtained basal spacing. Thermo-gravimetric analysis suggested improved thermal stability of the intercalated dye.