This research has two main goals: to develop an instrument for assessing Electronic Portfolio (ePortfolio) success and to build a corresponding ePortfolio success model using DeLone and McLean's information systems success model as the theoretical framework. For this purpose, we developed an ePortfolio success measurement instrument and structural model, at the individual level of analysis, using responses from 186 ePortfolio student users from higher education institutions worldwide. Academic institutions can use the results of this research to assess the success of their ePortfolio implementations from their students' perspective. The ePortfolio success model can also help to improve the implementation and use of ePortfolio systems through the analysis of the causal relationships of their different dimensions. Finally, initial guidelines about how to use the instrument as part of an ePortfolio system review process are also discussed. (Contains 9 tables and 3 figures.)