Thought the years, there have been improvements in the management of construction projects; however, the problems of cost overruns are still a critical issue in the construction industry. For this reason, this paper attempt to identify the main causes of cost overruns in construction projects in the United Kingdom and the Critical Success Factors [CSFs] that can help prevent these causes. This research carried out a literature review which helped to find the main causes of cost overruns in construction projects. In addition, the author also reviews some existent literature regarding CSFs. Most of this literature is concentrated on the Factors that influence the overall cost performance of projects; however no many studies have been conducted to identify the CSFs that have an influence in the cost performance of construction projects. For this reason, this dissertation aims to fill this gap, attempting to identify those factors that can prevent poor cost performance of projects. Though a positive approach, a multi-case study method was performed in this research. The multiple case methods was constituted of 6 different projects in the construction industry constructed by companies from the UK. Hence, two different hypotheses were tested and the conclusion suggested that there are certain Critical Success Factors that can help prevent the occurrence of cost overruns in construction projects in the UK. This exploratory research has not only filled the gap in the CSFs’ literature, but it has also suggest a list of CSFs that can be used to improve the cost performance of construction projects in construction companies and in this way avoid or reduce the occurrence of cost overrun.