Construction delays are one of the most common problems in the construction industry. Identifying major causes of delays is required to improve project management for improved schedule performance. Specific industry features and characteristics may create differences in delay causes across nations. The current work identifies the primary causes of delays in the construction phases of building construction projects in Palestine from the perspectives of clients, contractors and construction managers using a web-based survey of 10 practicing clients, 15 contractors, and 16 construction managers. Delayed progress payments by clients, client variations and changes of scope, delay in obtaining permits from municipality, exceptionally low bids, delays caused by subcontractors, rain effect on construction activities, difficulty in the transfer of equipment and introduced to the Palestinian territories (political conditions) were found to be the most important causes of delay. The methodology was followed is collecting data from field in different methods, and then analyze these data using Likert Scale to finally get sufficient results. Recommendations for improved performance and future research are discussed.