In today's constantly changing global business environment, understanding cultures have become essential and a prerequisite for business success. Understanding and successfully managing cultural differences can provide several advantages for project as well as company success. These concepts become more critical in construction due to the increase in strategic alliances in this industry. In this study, a part of the research that was conducted among 11 UK senior managers who have some years' of experience in international construction projects has been presented. One of the specific objectives of this study was to find out the opinions of managers about the relationship between management of cultural differences and project success. Within this context, semi-structured interviews were carried out with these managers. The interviews took place over a 3-month period between November 2007 and January 2008. Analysis of the qualitative data was performed using content analysis. Based on the findings, successfully managing cultural differences were seen as one of the key elements in project success. On the other hand, ignoring and mismanaging cultural differences were considered as one of the important causes for project failure.