The paper examines the issues of cost and time overruns in the context of construction activities in Mauritania. The construction industry as the main engine of economic growth faces the worldwide problems of delays and overspending. These challenges contribute to financial losses and project delays in the Mauritanian context hence the need to understand what causes them. The primary goal of this study is to determine and understand what causes cost and time overrun in project in Mauritania. Using both quantitative and qualitative research techniques, information was gathered via questionnaires from different construction stakeholders. The study employed descriptive statistics and regression in assessing relationships and the patterns between causes of overruns. This study presents a range of issues that have significant impacts on both costs and time overruns in the projects for example weak contract management, financial constraints, and changes in the project scopes among others. However, these factors were enumerated using the RII (Relative importance index). Another approach adopted is creating predictive models that help in anticipating time delays and the impact on cost overflows. They have good predictive power showcasing complex links between time and cost overruns. The study shows how crucial are good project and contract management, effective site management, and clear communication can be for reducing time overruns. The study further demonstrates strong positive relationships between the timing losses and costs overruns highlighting significance of the correct timing for costs controlling strategies. Keywords:- Time overrun, Cost overrun, impact, construction project, predictive models, Mauritania, Project management.