Hebron Municipality has a problem in finishing the construction projects in due time which has a negative impact on the success of these projects such as, exceeding the time limit, increasing the cost estimates. These negative effects reflect themselves on the different spheres of life and the whole society in general. It is important to investigate this phenomenon in the period between 2010-2014 through studying the causes behind it.
This research aimed to investigate the main causes of delay in the completion of construction projects in Hebron Municipality in Palestine, and to identify the average of time overrun. It also analyzed and ranked the most important causes of delay according to their frequency of occurrence, degree of severity and the important index from the point of view of contractors and consultants.
The method used for the analysis was mixed method research design (quantitative & qualitative) as a research approach for this research, while the interview tool and case study were selected to collect qualitative data and a questionnaire tool has been designed to collect the quantitative data. The field survey of a questionnaire contained (69) possible causes for the delay categorized into four major groups. The questionnaire was distributed to the sample of the study that included 24 participants, which is at the same time the population. The population included (16) contractors and (8) eight consultants which represents two main parties in construction projects, and the interview tool was selected to studying two cases with two projects exposed to time and cost overrun.
The research showed  delay in many construction projects conducted for Hebron Municipality during the period between 2010-2014, where there was a delay in ( 38) projects out of (74), and this represent (51.4%) of the projects. Moreover, the study indicated that average of time overrun is between (10% and 30%) of the original time of the projects. The study also showed that (41.7%) of the respondents believe that the main reason of the delay is the contractor. However, the results concluded that the following are the top five delay causes arranged according to the importance index:

1. The delay in paying the financial dues to contractors by the client.
2. Award project to lowest bid price (selecting the contractor who has the lowest bid).
3. The delay in due payments to the suppliers by contractor.
4. Difficulties in financing the project by the contractor.
5. Dispute with neighbors.