Digital teaching portfolios have been proposed as an effective tool for teacher learning and professional development, but there is a lack of empirical evidence supporting their effectiveness. This study proposed the design of a structured digital portfolio equipped with multiple aids (e.g. self-assessment, peer assessment, discussion and journal writing) for the professional development of teachers. This study also empirically evaluated the reflection and professional development as demonstrated in digital teaching portfolios with multiple supporting measures. Forty-four in-service substitute teachers participated in a course of classroom assessment and used a Web-based portfolio system. Based on the framework of teacher reflective thinking developed by Sparks-Langer et al., we found that most teachers demonstrated moderate levels of reflection in their journals but only one-third of them showed the highest level of reflection. We also found that the professional knowledge of teachers about classroom assessment--as shown by their implementation of it--improved significantly during the construction of portfolios. The above findings also represent good evidence that digital portfolios with multiple aids are beneficial to teacher reflection and professional development.