An investigation was undertaken to assess the combining ability, nature of gene action and heterosis with respectto grain yield and its component traits in 48 single cross hybrids of maize developed by crossing 16 lines and three testersin line x tester fashion in rabi 2017-18. These hybrids and parents were evaluated against three popular checks during kharif2018 under rainfed ecosystem. Analysis of variance revealed that mean sum of squares of parents and hybrids weresignificant for 13 characters which imply that presence of variability among the treatments. The contribution of femaletowards hybrid variance was higher than the males and line x tester interaction for all the characters except shellingpercentage. The gene action study revealed highest magnitude of non-additive gene action than additive gene action for allthe characters that were studied except days to 50 per cent tasseling, days to 50 per cent silking, days to 75 per cent brownhusk maturity and cob girth. The lines viz., NBPGR-1, NBPGR-7, NBGPR-8, NBPGR-9, NBPGR-11 and NBPGR-13were good general combiners for maximum number of yield contributing characters and the crosses GPBMH-1820 (NBPGR-9 x KDMI-16) and GPBMH-1836 (NBPGR-14 x CI-4) were superior with highest magnitude of per se performance alongwith significant positive SCA effects for most of the yield and yield contributing traits. The crosses viz., GPBMH-1820,GPBMH-1832, GPBMH-1803, GPBMH-1821, GPBMH-1802, GPBMH-1836, GPBMH-1843, GPBMH-1812,GPBMH-1831 and GPBMH-1811 were exhibited highest percentage of standard heterosis over the checks.