Among alternative types of assessment, Ipsative Assessment (IA), as a comprehensive form of dynamic assessment, has recently attracted a lot of attention among researchers. This study was an attempt to determine the effect of IA on English as a Foreign Language (EFL) learners’ argumentative writing components such as complexity, accuracy, and fluency (CAF). To so doing, 76 male and female EFL learners within the age range of 18-42 in a language institute in Tehran, Iran were selected out of 95 intermediate-level learners, based on their performance in a standard Oxford Placement Test (OPT). The selected participants were randomly divided into two groups; the experimental group (N = 40) received IA and the control group (N = 36) received teacher assessment. The study participants went through the process of pretesting, intervention, and post-testing. A measure of one-way Analysis of Covariance (ANCOVA) and a Multivariate Analysis of Covariance (MANCOVA) were run to probe the null-hypotheses. The results indicated that IA strategies had a statistically significant effect on EFL learners overall writing performance. In addition, the experimental group significantly outperformed the control group on the posttests of complexity, accuracy, and fluency, as L2 writing sub skills. The study raised some pedagogical implications for EFL teachers and learners such as using IA in the L2 classroom to enrich L2 writing development of learners and some for EFL syllabus designers to encompass IA in the syllabi they design for institutions and language schools. Also, some suggestions for further research were made.