<p>Fall armyworm (FAW), a latest introduce pest in India during 2018, is a highly destructive invasive pest of maize (<i>Zea mays</i> L.). It threatens to reduce maize productivity by around 80% across tropical regions. Being an economically significant pest, the traits imparting genetic resistance to this pest have not been studied so far. Our study aimed to decipher the genetic basis of resistance through generation mean analysis (GMA) using six generations (P₁, P₂, F₁, F₂, BC₁P₁ and BC₁P₂) developed from two crosses, i.e., CML71 × LM23 and CML67 × EML220. CML 71 and CML 67 were FAW moderately tolerant lines, and LM 23 and EML 220 were FAW susceptible lines. CML 71 and CML 67 were CIMMYT lines and are the only moderately tolerant lines reported to date. Evaluations of six generations were conducted under protected (insecticide-spray) and open (natural infestation) field conditions. Traits assessed included leaf injury at 14, 28, and 45 days after infestation (DAI) and cob injury. Results revealed that non-additive gene action, particularly dominance (h) and epistatic interactions (i and l), played a predominant role in the inheritance of insect resistance traits. Significant dominance and duplicate epistasis were frequently observed across developmental stages and environments, highlighting complex genetic control. The findings suggest that recurrent selection strategies would be more effective for improving insect resistance and yield stability in maize, particularly under variable infestation environments.</p>