This study was carried out in the Teaching and Research Farm of Delta State University, Asaba Campus from March 2008 to June 2010 to evaluate the response of grain weight of maize to variety, organic manure and inorganic fertilizer. The experiment was carried out in a Randomized Complete Block Design (RCBD) replicated three times in a factional layout. Four different rates of poultry manure, cattle dung and NPK 20:10:10 fertilizer were applied to three maize varieties sown at 75cm x 15cm and evaluated for the grain weight. The results obtained indicated that hybrid variety which produced yield of 2.1 tha-1 in 2008 and 2.3 tha-1 in 2009 was superior. The results of interaction showed that variety, manure type and rates of application were significantly (p<0.05) different in 2008 and 2009. Based on the findings of the study, it is recommended that (i) Hybrid maize variety, 9022-13, which was outstanding in grain weight be grown in the study area. Alternatively, farmers who prefer open-pollinated varieties could grow BR9922-DMRSF2 or Agbor local variety for farmers who prefer local varieties in maize production. (ii) Farmers who prefer mineral fertilizers for increased grain weight of maize should apply 450kgha-1 of NPK 20:10:10. (iii) Farmers who practice organic agriculture in Asaba agro-ecological zone should apply 30tha-1 of poultry manure to enhance maize yield.