This experiment was performed to evaluate heterosis and combining ability of morphological traits in maize (Zea mays L.). The experiment was arranged in randomized complete block design (RCBD) with three replicates. Twenty maize hybrids were obtained by 5×5 complete diallel crosses in first year and were evaluated for plant attributes like plant height, ear height, ear leaf area, flag leaf area, days to 50% silking, days to 50% pollen shed, anthesis-silking interval (ASI), no. of leaves per plant, no. of branches per tassel, no. of kernel rows per ear and kernels per row, 1000-kernel weight, shelling percentage, grain plus biological yield per plant and harvest index in second year. Among the crosses NCEV-4 × NCEV-3 (462.70g) showed maximum 1000-kernel weight, followed by NCEV-3 × EV-70040 (451.33g), while highest grain yield per plant was recorded for NCEV-4 × NCEV-3 (152.97g), followed by NCEV-3 × EV-70040 (145.10g). Maximum and highly significant heterosis and heterobeltiosis was found in cross NCEV-1530-11 × HNG (70.49 and 67.54), followed by HNG × EV-70040 (65.57 and 56.39) and HNG × NCEV-1530-11 (64.14 and 61.3), rest of the crosses also showed positive and highly significant heterosis and heterobeltiosis for grain yield per plant. Among the parents NCEV-3 has best GCA for grain yield (4.30) while cross NCEV-3 × NCEV-4 has best SCA for grain yield per plant (18.10) and could be used in hybridization for yield improvement.