This study presents a discussion of the C=O stretching vibrational band of methyl ethyl ketone using vibrational (FTIR and Raman) spectroscopy. The difference in the maxima of the spectral bands is 3.5 cm-1. Several reasons are given to explain the mismatch of C=O stretching frequencies and the difference in intensities of spectral bands. The geometry of various dimer and trimer aggregates of MEK was optimized at B3LYP/6–311++ G(d,p) level by Density Functional Theory method. Molecular electrostatic potential surface analysis was used to understand the electron density distribution in aggregates. It was determined that MEK dimers are formed by intermolecular dipole-dipole interactions by non-covalent interaction (NCI) and reduced density gradient (RDG) tools.