Abstract: This study applied Messick's unified, multifaceted concept of construct validity to an electronic portfolio system used in a teacher education program. The subjects included 128 preservice teachers who recently completed their final portfolio reviews and student teaching experiences. Four of Messick's six facets of validity were investigated for the portfolio in this study, along with a discussion of the remaining facets examined in two previous studies. The evidence provided support for the substantive and generalizability aspects of validity, and limited support for the content, structural, external, and consequential aspects of validity. It was suggested that the electronic portfolio may be used as one requirement for certification purposes, but may not be valid for the purpose of assessing teacher competencies.