Abstract: The use of e-portfolios for formative assessment in English language teaching has been well supported by literatures, yet, it is still underexploited in the context of Vietnam. The inclination to examination amongst Vietnamese people is believed to guarantee great opportunities; thus, it is not surprising to see that curriculums are saturated with tests such as short and long quizzes, periodical and summative tests. Unfortunately, test-oriented curriculums bring negative backwash towards teaching and learning, as well as affecting students' overall achievement. To address the issue on the negative backwash, laborious and ineffective error correction, and other emerging issues relevant to the traditional formative assessment in writing, collaborative e-portfolio project was initiated. It is aimed is to replace periodic tests and help reinforce formative assessment in an academic writing held in university in Hanoi, Vietnam. Data were collected from two experimental groups' reflective essays, an entry on their e-portfolios, which were analyzed through thematic analysis. Finally, after assessing the innovative practice through Kirkpatrick and Kirkpatrick (2006) four level of program evaluation, it was found that students have enjoyed the project, learned necessary skills for writing, improved attitude towards learning, and have achieved the course learning outcomes.