Dynamic assessment (DA) integrates assessment and instruction between the instructor and learners. It emphasizes the learning process. DA was introduced to 24 undergraduates and 9 graduate students in two academic writing courses in Taiwan. The analysis of the pre- and post-tests, writing portfolios, observations, and interviews reached the following major conclusions. First, participants had a positive attitude toward DA, particularly regarding expert evaluation as the mediation for identifying global and local errors. Secondly, the integration of DA influenced the participants' academic writing on research proposals, particularly the structure and the use of the APA format. Thirdly, participants regarded the instructor's model writing and the exemplary journal articles as useful mediations. Suggestions on the effective integration of DA into academic writing courses are provided.