The present study investigated the impact of bilingual education on language achievement of Iranian Pre-intermediate EFL learners. It actually used bilingual education through content- based methodology or subject matter such as math, science and reading. To this purpose, the researchers used 40 Pre-intermediate EFL participants who were studying English conversation at a private language institute in Sari. These learners were chosen and divided randomly into control and experimental groups. Both groups took the same test as a pretest. The experimental group had access to bilingual education methodology through math, science and reading, while in the control group, participants had no special treatment. They had just access to the conversation by the use of conversation methodology which was assigned by the institute curriculum. After nineteen sessions, the posttest was administrated to both control and experimental groups. Based on the obtained results, a significant difference was observed between the mean scores of the two groups on the posttest. In fact, the null-hypothesis was rejected as the experimental group performed significantly better on the posttest.
