Construction delay considered as one of the most recurring problems in the implementation of construction projects.It is widely known to have an adverse impact on project success in terms of time, quality and cost. The effect of construction delay is not only confined to the construction industry, but also its influence on the overall economy of a country like Ethiopia. This research was conducted to assess the causes of excessive delays in the completion of road project during the construction phase due to the failures of Employer, Consultant, and Contractor in Addis Ababa City Road Authority projects. Spearman rank correlation coefficient from the Relative Importance Index (RII) analysis was used to test the agreement between different groups of respondents participated in the questionnaire survey, and to rank the three construction parties according to their responsibility area and importance as perceived by the respondents which factor causing the delay of road projects. This research identified sixty-five (65) causes of delay. There were fifty-one (51) valid questionnaires which received back from Contractors, Consultants, and Employer (AACRA). Based on the results, the contractors have the highest percentage of responsibility area that causes the delay of about 40%. While the second was on the part of the Employer, which comprised of 26.15%, and the consultant which placed third of 23.08%. On the other hand, there were 10.77% of the respondents attested that the Shared groups (3-parties) have the responsibility area which causes project delay during the implementation phase. About this, the research study identified and ranked top ten factors causing delays of construction projects in Addis Ababa City Road Authority. Poor ﬁnancial control of the project ranked 1st with Relative Importance Index (RII) of 0.905. Difficulties in financing project by contractor ranked 2nd with Relative Importance Index (RII) of 0.854. Type of project bidding and award (lowest bidder) ranked 3rd with RII of 0.850. A poor site management and supervision of contractor ranked 4th with RII of 0.839. Selecting inappropriate contractors ranked 5th with RII of 0.823. Lack of hightechnology mechanical equipment ranked 6th with RII of 0.819. Inaccurate initial project scope estimate and Ineffective project scheduling ranked 7th and 8th with RII of 0.803. Weak control of the project progress ranked 9th with RII of 0.788. And the Contractor’s staffis not adequately trained in professional construction management techniques ranked 10th with RII of 0.784. Therefore, it concluded that the main party Contractor did not perform properly his duties and obligations leading to the main contributory factor causing the failure of the project. Index Terms— Construction delay factors, Contractor, Consultant, Employer, Responsibility area, Road projects, Relative Importance Index.