The significance of alternative assessment in second language (L2) has been widely acknowledged in the literature. However, the implementation of alternative assessment in English as a Foreign Language (EFL) context has not been much welcome by L2 educators and practitioners. The aim of the present research was set to explore the impact of implementing self-assessment and peer-assessment practices on writing performance and writing self-efficacy of EFL learners in Iran. A total number of 36 homogeneous intermediate learners were selected as the participants who were then randomly assigned to a self-assessment group (N= 17) and a peer-assessment group (N= 19). As for the treatment of the present study, the participants of the self-assessment group were taught to self-assess their writing tasks, whereas the participants of the peer-assessment group were taught to assess the writings of their peers. Two timed-writing essays and the Writing Self-Efficacy Scale (WSES) were administered to collect the data. The results obtained from performing paired-samples t-tests and ANCOVA indicated that both self- and peer-assessment activities significantly contributed to improving writing performance and writing self-efficacy of the participants. It was revealed that the participants of the peer-assessment group performed better than those in the self-assessment group in terms of both writing performance and writing self-efficacy, showing that peer-assessment activities were more effective than self-assessment activities in increasing writing competencies and self-efficacy of the participants.
