Individual and collaborative assessments have engaged all researchers' attention over the last century. This study explored the probable improvement in Iranian EFL learners' writing with respect to individual and collaborative self-assessment training as well as examining the effect of gender on assessment training. The participants in this study were 80 (40 males, 40 females) English learners in a language institute. This sample was divided into four equal groups. Two groups worked on assessment individually, and two groups performed assessment collaboratively. Data were collected from a self-assessment questionnaire and writing scores based on IELTS task 1 writing band score descriptors and Magoosh Essay Rubric for the GRE and GMAT. Results revealed the positive effect of collaborative assessment training on writing. Additionally, the Two-Way Analysis of Variance (Two-Way ANOVA) indicated that the female participants in the collaborative group outperformed males in the same group. The study provides implications for teachers and institutional policymakers in how to improve English learners’ writing proficiency.
