Abstract: The present study was conducted to evaluate 45 hybrid rice along with currently available six semi-dwarf, early to mid-early duration and high yielding indicas (Govind, Manhar, Pant Dhan 4, Sarjoo 52, Pant Dhan 12 and Narendra 359) along with four tropical japonicas cultivars (BSI10, BSI16, B4116 and B4122) having wide compatibility gene(s), in relation to analyze gene action and heterosis for grain yield and associated traits. The experiment was conducted in randomized complete design and data collected on various traits were analyzed for heterosis and combining ability. Both additive and non-additive gene action were found to control the expression of all characters. The ratio of General Combining Ability (GCA) to Specific Combining Ability (SCA) variances exhibited greater relevance of non-additive gene action governing yield and its associated traits. Parent B4122 and Sarjoo 52 were found to be the best general combiner for maximum characters, including grain yield plant-1. The crosses B4116xSarjoo 52, BSI10xPant Dhan 12, BSI10xNarendra 359, B4122xManhar and B4122xGovind recorded the highest SCA effects for yield plant-1. Heterosis over mid-parent, better parent and standard variety ranged between -54.17 to 169.70, -58.31 to 150.32 and -64.55 to 146.15%, respectively. The trends of magnitude of heterosis for grain yield and plant height were I/J>I/I>J/J and for days to 50% flowering I/J>J/J> I/I hybrids. The crosses B4116xSarjoo 52, BSI10xPant Dhan 12 and BSI10xNarendra 359 were identified as the best hybrids on the basis of per se performance, high heterosis and combining ability effects. Most of the heterotic cross combinations identified in this study involved indica and tropical japonica lines having wide compatibility gene as their parents. Interspecific hybrids exhibited high heterobeltiosis and economic heterosis.