Langmuir-Blodgett (LB) films of a charge-transfer complex of 2-octadecyl-7,7,8,8-tetracyanoquinomethane (octadecyl-TCNQ; Figure 1) and malachite green (MG; Figure 1) have been prepared from an adsorption Langmuir monolayer and their molecular orientation and structure have been explored by visible-near-infrared and infrared spectroscopy. The infrared spectra of the LB films of octadecyl-TCNQ/MG show two bands at 2222 and 2178 cm-1 assignable to C=N stretching modes. The appearance of the lower-frequency band and its frequency suggest that the charge-transfer complex is formed by the adsorption of MG to octadecyl-TCNQ on an aqueous subphase and the degree of the charge transfer is nearly complete; i.e. TCNQ- is formed. The visible-near-infrared absorption spectrum of the LB film of octadecyl-TNCQ- species. The infrared and visible-near infrared spectra of MG do not undergo a significant change upon the formation of charge-transfer complex, indicating that the structure of MG in the complex is very close to that in a solid state and that the interaction betweeen MG and octadecyl-TNCQ is very weak. Comparison between infrared transmission and reflection-absorption (RA) spectra of the LB films of octadecyl-TCNQ/MG indicates that the hydrocarbon chains are tilted considerably with respect to the surface normal while the TCNQ planes are nearly perpendicular to the substrate surface at least above the third monolayers. The infrared spectral also suggest that the molecular orientation and structure of the TCNQ part resemble each other between the LB films of octadecyl-TCNQ/MG and those of octadecyl-TCNQ, but the molecular axis of the TCNQ chromophore is less tilted in the former than in the latter.