Organizations are faced with these fundamental questions: what relation is there between each E-Procurement’s dimensions and organizational performance? And how organizations can set the optimal level of multiple dimensions of e-procurement? In this study, initially, the affecting dimensions of electronic procurement have been extracted from the previous literatures which have tended to use one-dimensional concept of procurement, then their simultaneous impact on organizational performance were assessed. This study is a survey. Information is collected by a questionnaire. The questionnaire reliability is measured through Cronbach's alpha, its construct validity measured by the confirmatory factor analysis and its content has the validity. Iran's top 300 companies were selected as the statistical population and 177 companies out of those completed and returned the questionnaires. In order to assess the causal correlation relationship between dependent and independent variables of twenty hypothesizes, types of parametric tests including multiple regression, path analysis, factor analysis and one-sample T-test were used. Results explain the impact of Volume, Diversity, Breadth and Depth as dimensions of e-procurement on cost reduction, internal efficiency, administrative efficiency and improve coordination.