In spite of the scarcity of study on the cost effect of design error induced variation on roadrnprojects, the study has investigated the very causes of design error induced variation, the frequentrndesign errors that lead to variation, the cost effects of design error on the variation costs, andrnmitigations for design error induced variation in selected Ethiopian road projects. A two foldrnmethod of research (Questionnaire survey and Case study road projects) was applied inrncollecting the necessary data for the research through a purposive sampling technique. Arnspecially designed survey questionnaire was distributed and collected from 25 project delegatedrnrespondents to fill out project-specific sections of the questionnaire as well as the industryrngeneric questions for further analysis. The finding revealed that Inexperience of designers, Lackrnof knowledge, Lack of integration/coordination between designers of different disciplines, DesignrnCost, and Duration of Design are the top five causes of design error induced variation. Thernfinding further ranks the frequency of occurrence of design errors based on design elements in thernordered as Vertical Alignment, Horizontal Alignment, Minor Drainage, and Pavement. Moreover,rnout of the total variation cost in road projects, 43% is influenced by design errors with majorrncontributions of Horizontal Alignment and Minor Drainages Accounting 50% of the cases amongrnothers. Finally, based on the analysis of the results, recommendations have been proposed thatrnenables to minimize design error which has the potential to result in variation costs.