Obesity and non-alcoholic fatty liver disease (NAFLD) affect expression and function of cytochrome P450 genes (P450s). The increased expression of inflammatory cytokines is a major driver of the down regulation of P450 expression in NAFLD. Decrease in P450 expression could potentially lead to drug-drug interaction, inefficient pharmacological effect of a drug or hepatotoxicity. An epigenetic modifier, a histone methyl transferase enzyme G9a, known to increase histone 3 lysine 9 (H3K9) methylation, is down regulated in diet induced obesity animal models. In a liver specific G9a knockout animal model, expression of P450s was down regulated. Currently, the role of G9a in regulation of P450s in steatosis is unknown. Our hypothesis is that, in steatosis G9a plays a role in down regulation of P450 expression. In this study, we used HepaRG cells to induce steatosis using a combination of free fatty acids oleic acid and palmitic acid. The G9a was knocked down and overexpressed using small interfering RNA (siRNA) and adenovirus mediated approaches, respectively. Knockdown and overexpression of G9a in the absence of steatosis decreased and increased expression of nuclear receptors constitutive androstane receptor (CAR), pregnane x receptor (PXR), small heterodimer partner (SHP), and CYP2B6, 2E1, 2C8, 2C9, and 3A4, respectively. In steatotic conditions, overexpression of G9a prevented fatty acid mediated decreased expression of CAR, CYP2C19, 2C8, 7A1 and 3A4. Our current study suggests that G9a might serve as a key regulator of P450 expression at both the basal level and in early steatotic conditions. Single nucleotide polymorphism of G9a leading to loss/ gain of function could lead to the poor metabolizer or ultra-rapid metabolizer phenotypes.