The present study compared two modes of peer feedback, i.e. asynchronous computer-mediated feedback (ACMF) and face-to-face peer feedback (FTFPF), to assess outcome related to writing self-efficacy beliefs, self-regulation, and writing. A total of 268 students were allocated to three groups, namely an ACMF group, an FTFPF group, and a control group of not receiving peer feedback. The intervention lasted a semester. Data collection included pre-and-post surveys and writing tests. The survey measured students' writing self-efficacy beliefs and self-regulation. The writing assessment specifically targeted the proficiency in composing an argumentative essay. The findings revealed that the ACMF group showed the greatest increase in EFL writing self-efficacy beliefs, self-regulation, and writing performance. The participants' EFL writing self-efficacy beliefs and self-regulation also influenced their writing performance. Relevant pedagogical and research implications were discussed based on the findings.