This study examined the types of heuristics that valuers adopted, the factors that influenced their adoption and their impact on valuation accuracy of commercial properties, with a view to improving valuation practice in Nigeria. The study used both the survey and quasi-experimental methods. The survey method adopted questionnaire which were administered to all the 54 estate surveying and valuation firms in Ibadan while 10 (18.5%) in the category of principal partners/branch managers of the firms were orally interviewed. The information collected included: profiles of the estate firms, commercial property valuation procedure, level of awareness of valuation accuracy, and the significance of valuers' behaviour on valuation outcomes. The quasi-experiment was carried out using a simulated valuation of a commercial property in Ibadan (a familiar location). The results of the Chi-square test (32.000) at P 0.05 indicated that heuristic adopted by the valuers in the study area did not appear to affect the level of valuation accuracy of the commercial properties. This was also exhibited by 1.08% variation between the simulated valuation outcomes and the market price.