Completing construction projects on-time, within budget, scope and within the specified standard successfully is a major problem. Among these, time and cost overrun are frequently happens especially if the project is a mega project in developing country. The main aim of this research is to identify the key factors affecting time and cost overrun, asses its impact and identify the possible measures to minimize time and cost overrun in mega sugar projects in Ethiopia. The research uses interview, desk study and questionnaire survey for data collection. The analysis are made in two parts interview and desk study on one part and questionnaire survey on the other. Poor feasibility study and site investigation, Improper planning and designing, Capacity limitation, Poor procurement system, Contract management problem are among the main time and cost overrun contributing factors obtained from interview and desk study. While Improper planning and scheduling, Unrealistic contract duration, Improper and poor project feasibility study etc. are some of time overrun factors and Poor project (site) management/ Poor cost control, Wastage, Construction Cost Underestimation etc. are among the list of the main cost overrun factors from questionnaire survey. And effects like; less return on investment for client, high price of sugar for end user, Abandoned and termination of project are observed on the project due to the problem of time and cost overrun. Finally, feasibility study related, Service and infrastructure related, design and planning related, stake holder management related, procurement and contract management related, Capacity building related and Human resource management related recommendations are given.