Indole derivatives represent an important class of privileged structures. Spectroscopic (Fourier transform infrared (FT-IR), FT-Raman,¹H and [Formula: see text]C nuclear magnetic resonance (NMR)) investigations of the indole-bearing title compound, namely 5-methoxy-1-[(5-methoxy-1[Formula: see text]-indol-2-yl)methyl]-1[Formula: see text]-indole (MMIMI) have been carried out. The corresponding data of the MMIMI molecule were analyzed to understand its optimized geometry, and inter/intra-molecular interactions. The equilibrium geometry, harmonic vibrational wavenumbers, Frontier orbital energy, and natural bond orbital (NBO) analyses have been performed with the help of density functional theory (DFT) with B3LYP/6-311[Formula: see text]G([Formula: see text],[Formula: see text]) level of theory. The vibrational modes have been unequivocally assigned using potential energy distribution analysis. The theoretically predicted wavenumbers have good agreement with the experimental values. NBO has confirmed the intra-molecular charge transfer interactions. HOMO–LUMO analysis was carried out to explore charge delocalization on the MMIMI molecule. The immunomodulatory activity of the title molecule was predicted using molecular docking approach.