Standardized portfolios are being used by teachers and teacher candidates to demonstrate subject matter knowledge for certification or to be considered highly qualified; however, the psychometric adequacy of data used for this purpose has not been evaluated. In the current study, we examined the interscorer reliability, concurrent, predictive, and discriminate validity, and instructional utility of an assessment portfolio used in a special education teacher education program. The estimate of interscorer reliability was .91, validity coefficients ranged from .53 to .60, and the discriminate validity coefficient was 2.01. A comparison of scores for instructional objectives suggested relative difficulties writing adequate short-term objectives, which was then further emphasized in subsequent instruction and resulted in increased scores. Suggestions for practice and future research are included. (Contains 3 tables.)