This study seeks to investigate the impact of symmetrical (S) and Asymmetrical (AS) scaffolding, which are two types of scaffolding, on students' reading comprehension achievement of English as a Foreign Language (EFL). The study was done in two phases: In the first phase after administering a Pre-test, 52 homogeneous intermediate students were selected, and they were divided into two experimental groups. The experimental group (A) received instruction according to S strategy whereas the experimental group (B) was instructed via the AS strategy. A Post-test was administered, and its results were analyzed through t-test. The results indicated that although S scaffolding has significant effect on learners' performance in reading comprehension, enhancing it but AS scaffolding is a more effective strategy in improving reading comprehension achievement. In the second phase, the qualitative data consisted of a total of 60-minute recording of 28 participants' interviews. The results have been more consistent with Vygotsky's theories than with those of Piaget in cognitive development.