The key character of the construction projects is complexity where many human and non-human factors and parameters play vital roles. This study discusses causes of change orders, their impact on projects performance and methods of control in Oromia roads authority projects using a combination of questionnaire and 13 project’s case studies. As a result, the most common reasons of causes of change order categorized as change order by requirement, change order by emergent, change order by defect in contract document and change order by defect during construction work. These studies covered four asphalt and nine gravel road projects awarded by Oromia roads authority. The projects used for analysis were projects awarded between 2013 and 2019 G.C. Analysis of both case study and questionnaire made by SPSS in which independent t-test, one-way ANOVA and Univariate methods used. Out four major causes of change order’s frequency of occurrence, 66.30 percent caused by defect in contract document. Cost wise also, 58.75 percent of total amount of change order were by defect in contract document and 34.09% were change order by emergent. From respondent’s response analysis, 69.1% of the respondents strongly agreed that defect in contract document is the main cause of change order. From the total change orders encountered by defect in contract document 54.70 percent of the change orders caused by lack of required data including design data, 31.55 percent occurred due to error in design (addition and omission in design), 12.83 percent resulted from inaccuracy of quantity under BOQ and the rest caused by noncompliance of design with the owner’s requirement. Concerning root cause of change order by emergent unforeseen conditions or differing site condition (100% total change order by emergent) was the leading root cause. Even though the redundancy of change in Babich – Mugno project was maximum (13.04% of total change frequency), total change order amount was maximum for Adele-Sekina project, which is 20.36% of total change order amount. Earthwork is the most sensitive item to change, in which 69.85% of total change order amount was on earthwork item. The second item sensitive change order was drainage work, which covered 19.96% of total change order amount. Concerning causes of change on items, 86.24% of total change order amount in drainage work and 51.51% of total change order amount in earthwork were because of defect in contract documents. The major impacts of the change order were increase in project cost and delay completion schedule; kito-Furdisa, Jimma town asphalt, Negele borena asphalt, Babich-Mugno and Ambo kara were highly delayed projects in which 483.89%, 238.7%, 187.5%, 183.7% and 177.8% were their time progress respectively. Regarding over budgeting Kito-Furdisa,Babich-Mugno and Ambo-Kara were highly over budgeted projects in which 196.29%, 145.51% and 142.32% were their financial progress respectively. Again from respondent’s response also, increase in project cost (78.3% of the respondents strongly agreed) and Delay completion schedule (80.9% of the respondents strongly agreed) were the main impact of the change order. Regarding consequential impacts, 86.2% of the respondents strongly agreed that doing design review before construction contract award is greatest way of change order control. In general, design review before construction contract award, owner’s involvement at detail planning and design phase and clearing the site from right of way problems before construction were the core way of controlling change orders on road construction projects in Oromia. Therefore, as recommendation it have to be mandatory to rectify designs and clear the site from right of way problem before commencement of construction work.