This study determined the influence of estimating practice on cost performance of building projects. The objectives were to identify the estimating practices used by cost consultants, appraise the critical factors influencing estimating practice used, and to determine the influence of estimating practice on cost performance. The study involved survey design administered to engineers, builders and quantity surveyors in Akwa Ibom state, Nigeria. Data analysis involved descriptive statistics and Spearman Ranked correlation test. The findings of the study revealed the critical factors influencing estimating practice as complexity of design and construction, scale and scope of construction, method of construction and construction technique, tender period and market condition, and site constraints (access and storage limitation. The test of hypothesis indicated non-relatedness of estimating practice with cost deviation. There is therefore no significant correlation between estimating practices and the performance building works estimate for all category of buildings studied. The implication is that, estimating practice (method) adopted in budget estimation cannot influence the cost performance of building projects.