Abstract This research experiment took place at the Second Agricultural Research and Experiment Station of the College of Agriculture of Al-Muthanna University, located to the southeast of Al-Muthanna Governorate. The experiment was aimed at identifying potential parent lines and hybrid combinations with superior performance in terms of yield per plant and late blight disease resistance (Phytophthora infestans) in tomato (Solanum lycopersicum L.) with the goal of developing fifty F₁ hybrids from five distinct lines and ten testers through a Line x Tester mating design, to estimate heterosis for ten quantitative characters associated with yield and yield-related characteristics. The results indicated significant standard heterosis for plant yields with late blight disease resistance in the hybrid combinations Arka Meghali x LA 0475, EC 771585 x LA 0475, EC 771594 x LA 2138-A, and EC 771594 x CLN 13149. In addition, compared with the more productive parent, the hybrids EC 771585 x LA 0475 and Arka Vikas x LA 1713 produced significantly greater yield per plant (i.e., heterobeltiosis). Four hybrid crosses (i.e., Arka Meghali x LA 0475, EC 771585 x LA 0475, EC 771594 x LA 2138-A, and EC 771594 x CLN 13149) have been identified as potentially producing commercially viable hybrid seed due to their combination of high yields per plant and resistance to late blight. It is recommended that these hybrids be trialed in a second growing season, followed by multi-site testing, in order to further evaluate their stability and performance prior to commercial release. Keywords: Heterosis; Tomato; yield; Disease resistance