This study was conducted to investigate combining ability and gene action of rice hybrids and their parental lines. Four CMS lines as female parents and three restorers' lines as male parents were hybridized to produce  12 F₁ hybrids were used in a line x tester mating design. the resulted genotypes were used to estimate combining ability, heterosis, and gene action for yield and yield components characters. The results indicated that most characters  were largely governed by additive gene action. General and specific combining ability effects of the genotypes for the characters under study were estimated. The results showed that the characters were controlled both general combining ability (GCA) and specific combining ability (SCA) . The CMS and restorer lines showed variable  effects for GCA. The study also indicated the presence of  heterosis  over the better parent (BP), Mid-parents (MP) and over the best check variety Giza 178 for nine characters of yield and yield components.