Since an important role for working memory has been found in the first language acquisition (e.g., Daneman, 1991 Daneman & Green, 1986 Waters & Caplan, 1996), research on the role of working memory is emerging as an area of concern for second language acquisition (e.g., Atkins & Baddeley, 1998 Miyake & Freidman, 1998 Robinson, 1995, 2002, 2005). The present study focused on the role of working memory capacity in the development of second language reading ability. 55 L1 Persian EFL learners at three proficiency levels from a private language school participated in this study. They completed a battery of reading and working memory measures. Memory measures included phonological short-term memory, and reading span test (RST). Reading measures included two expository reading comprehension tests. Multiple regression analysis was applied to determine whether there are any significant relationships between working memory capacity and reading measures. Results of this study indicated a significant relationship between working memory capacity (as measured by RST) and reading ability at lower levels of proficiency.