Ten yellow kernel maize inbred lines were crossed during spring season 2019, in a complete diallel fashion to developed 90 F1 hybrids at Cereal Crops Research Institute (CCRI), Pirsabak - Nowshera, Khyber Pakhtunkhwa, Pakistan. During subsequent summer season 2019, ten parental inbred lines, 90 F1 hybrids along with two commercial checks (commercial hybrid CS-2420 and commercial OPV-2011Y) were grown in a randomized complete design with two replications. The objectives of the research were to study the mean performance of F1 hybrids in comparison to parental inbred lines and check genotypes, various categories of heterosis. Highly significant variations were recorded among the genotypes for all the studied traits except anthesis silking interval. The F1 hybrid exhibited less days to 50% tasseling, anthesis and silking i.e., 53.50, 56.00 and 59.00 days, respectively. Maximum primary leaf area was observed in F1 hybrid (659.34 cm2) whiles less days to physiological maturity were recorded in F1 hybrid. The F1 hybrids showed maximum values for kernels per row (42.50), and grain yield (8392.78 kg ha-1). Results obtained could be used for the development of early maturing and high yielding maize genotypes in future breeding programs.