Monolayer properties of 2-(3,4,5-tris-dodecyloxyl-phenyl)-[1,3,4] oxadiazole based "tripod" dye molecules, P2G, have been studied by Langmuir–Blodgett technique, UV and polarizing microscopic images. Pressure-area isotherm of P2G has transition at 17 mN/m and this transition is believed to be the orientation rearrangement of the molecules from perpendicular to horizontal with respect to the surface normal. The presence of water insoluble hydrophobic single alkyl chains causes restructuring edge-on orientation and aggregation by compression. The H-aggregated structure was observed by UV spectrometer, and the orientation effect was clearly observed by polarizing microscopic images and sum frequency generation.