This study examines and analyses the variation factors of project plan and their contributions to project failure. The slippage of project plans with respect to budget, schedule and quality specifications are indicators of poor performance and imminent failure. The primary data used for the study were captured by field survey on some construction firms based on their experience and perceptions on the subject matter. The methods of multiple regression and correlation analyses were the analytical tools used for the data analysis and statistical test of hypotheses. The results of the analyses indicate that design errors, management problems and resource delivery constraints are the significant variation factors of plan that contribute significantly to project failure. The study therefore recommends evaluation of design effectiveness, prior to project implementation, adoption of material requirements planning principles, and institution of corporate policy for periodic and comprehensive human resources development programmes.