Because of its contribution to economic development and economic activity, the construction sector in Ethiopia has a significant impact on national growth. Various studies, however, reveal that variation of work is one of the key factors contributing to time and cost overruns, disagreements among parties, rework, and poor work quality. The fundamental purpose of this research is to identify and analyze the major causes and impacts of variation of work on public building construction projects in Gondar City. To achieve the objective of this study, 51 major causes and 14 impacts on the variation of works were identified, and 22 causes and 12 impacts were refined based on expert recommendations. The data collection methods used were questionnaire surveys, case studies, and interviews. A questionnaire survey was used for a total of 135 respondents to model the cause factors of variation of works using a structural equation modeling approach through the Analysis of Moment Structure software package. The relative Importance Index is used to rank the mitigation strategies of variation of works. In addition, a detailed archive record assessment was carried out to determine the cost and time implications of the variation of works. For data reduction, identification of factor structures, and validation of study outcomes, both exploratory and confirmatory factor analysis methods were applied. According to the research findings, the major causes of variation of works are change of scope, financial problems, change in specifications, the inadequate scope of work, inappropriate use of the advance payment, design discrepancies, differing site conditions, technology change, inflation, and corruption. However, the most common impacts of variation of work are an increase in project cost, a delay, poor quality, low productivity, and disputes among professionals. The maximum cost overrun and time overrun are 59.13% and 690.42%, respectively, as compared to the original contract price and original contract time. Mitigation measures variation of works are the client should provide a clear brief of the scope of work, and the consultant should produce a concluding designs and contract documents. Effective communication between contracting parties prevents disputes. The study's findings are expected to assist construction organizations, practitioners, and policymakers in identifying the key factors influencing the variation of work in the construction of public building projects in Ethiopia. vi Keywords: Gondar City, Public Building Projects, Variation of Works, Cause and impact, Structural Equation Modeling, Factor Analysis