Ten diverse genotypes of rice (Oryza sativa L.) were crossed in a diallel fashion to study heterosis for 12 quantitative characters. In which for grain yield per plant all the 45 hybrids exhibited positive significant heterosis over mid parent and 37 hybrids exhibited positive significant heterosis over better parent. For straw yield per plant out of 45 crosses, 44 exhibited positive significant heterosis over mid parent and 42 exhibited positive significant heterosis over better parent. For total biological yield per plant out of 45 hybrids , 43 crossses exhibited positive significant heterosis over mid parent and 31 hybrids exhibited significant positive heterosis over better parent. For harvest index out of 45 crosses 25 showed significant positive heterosis over mid parent and 20 hybrids exhibited significant positive heterosis over better parent. The estimate of relative heterosis and heterbeltiosis provide information about the type of gene action involved in expression of various quantitative characters. The information of gene action helps in the selection of breeding methods for genetic improvement of the population.