Luminescence enhancement effect of Tb(TTA) 3 Phen (TTA=2-thenoyltrifluoroacetone; Phen=1,10-phenanthroline) on Eu(III) in Langmuir–Blodgett (LB) films was studied in this paper. Luminescent films with strong intensity were assembled by mixing Eu(TTA) 3 Phen with different molar percentages of Tb(TTA) 3 Phen with the help of arachidic acid (AA) (AA/complexes=1:1, in molar ratio). Meanwhile, the film-forming behaviors of monolayers were observed on a corresponding composite subphase saturated with film-forming material(s), TTA and Phen. The monolayers and LB films were characterized by UV-Vis spectra and fluorescence microscope photographs. The results show that they are homogenous and can be transferred onto the substrates successfully. Finally, the mechanism of luminescence enhancement effect of Tb(TTA) 3 Phen on Eu(III) caused by intermolecular energy transfer in the films was suggested.