The Fall Army Worm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), has been detected as a new exotic invasive pest in Egypt at the end of 2019 and it has become the most economically destructive pest of maize crop in Egypt. The main objective of current work is to study the effect of four constant temperatures (20, 25, 30, 35±1°C) on the biological attributes of FAW. The overall total developmental period of FAW was negatively correlated to the increase of temperatures being longest 27.37 days at 20°C and shortest of 15.53 days on 35°C. Lifetime fecundity of FAW was also significantly affected by temperature, the mean daily fecundity of FAW was 23.42, 66.17, 134.33 and 175.67 eggs/female at 20, 35, 30 and 25°C, respectively. Longevity of either males or females decreased as temperature increased. Generation survival rates was highest (83.33%) at 25°C and lowest (70%) at 30 and 35°C. At 20°C, the generation survival rates were 60.00%. Thereupon, the optimum temperature for population growth of S. frugiperda ranged between 25 to 30°C.