Construction industry is one of the most significant industries that growth rapidly to develop countries. These construction industries facing many problems the most common are delay and cost overrun. However, studies show that in OMAN rarely projects are completed within stipulated budget and time. This study is focusing on identification of significant causes affecting construction cost and time in Oman projects. The data of delay and cost overrun factors were collected through questionnaire distributed among the construction experts who involved in the current construction projects in Oman. The survey was carried out by interviewing respondents from consultants, contractors and client¿s parties. The collected data were analyzed by using Average Index method for each factor and these factors were ranked based on the index to determine its significance. The findings will help construction industry to avoid and reduce the Dekay and Cost overrun in future projects.