This study aimed to evaluate eight inbred lines of red and yellow maize and their half-diallel crosses and estimate of heterosis for earliness and morpho-physiological traits under normal and water-stress. Mean squares due to maize genotypes and their partitioning into parents, crosses and parents vs. crosses (P × C) were significant or highly significant for all traits under normal and water stress conditions, indicating wide diversity among parental material and enough genetic variability adequate for further biometrical assessment, and presence of significant heterosis under both irrigation treatments. P5 (L-49) and P7 X P8 under normal, P2 (Red-B) and P6 X P8 under water-stress were the earliest genotypes in anthesis and silking dates and anthesis-silking interval (ASI) when compared to other genotypes, which would be a good indicator for earliness. There were 17 and 11 crosses for anthesis date, 14 and 8 crosses for silking date, 23 and 9 crosses for ear position, manifested negative significant or highly significant heterosis over mid and better parents, respectively under drought-stress condition. There were 26 and 20 crosses for chlorophyll content, 12 and 4 crosses for ear leaf area, all the 28 evaluated crosses for stem diameter and biomass yield/plant, recorded highly significant positive heterosis relative to their mid and better parent, respectively under drought-stress condition. The highest positive heterobeltiosis were recorded by the crosses, P3 X P5 (476.35%), P4 X P8 (503.49%) and P5 X P8 (469.06%), and therefore, these crosses could be considered the best cross combinations for producing high biomass yield/plant.