Electronic portfolios (e-portfolios) have grown in popularity in ESL/EFL writing instruction for their contributions to students’ writing. However, selecting an electronic tool in e-portfolios is of concern to many researchers and teachers. The combination of Facebook and e-portfolios is a rather new implementation in educational research, especially in high school contexts. Therefore, the current research aimed at exploring (1) high school students’ perceptions of the use of Facebook-based e-portfolios in terms of their contributions in writing, and (2) problems in using Facebook-based e-portfolios in writing. Fifty grade 11 students at a high school in Soc Trang province, Vietnam participated in the research. Both quantitative and qualitative data were collected by using close-ended questionnaire and the interview. Prior to data collection, the students spent six weeks writing on Facebook close-typed groups. The results showed that the students highly appreciated the contributions of Facebook-based e-portfolios in terms of enhancing interaction, giving and receiving feedback, motivation and confidence in writing, writing skills, vocabulary, and grammar knowledge. No significant problems were found in using Facebook-based e-portfolios. The research is expected to shed light on implementing Facebook-based e-portfolios in improving the quality of teaching EFL/ESL writing in high school contexts.