The present study attempts to employ orthographic knowledge enhancement as a tool in order to determine its efficiency in improving Iranian EFL learners' reading comprehension. Orthographic knowledge can be defined as one's familiarity with the general spelling rules of a language, or the ability to defer those letter combinations that are permissible form those that are not, which makes it an exceptional requirement for effective word identification and as a result successful reading comprehension skill. In doing so, 55 male and female students learning English at preintermediate level in a language institute in Astaneh, Guilan, Iran were randomly selected and were equally divided into an experimental and a control group. A researcher-made reading comprehension test followed by multiple-choice items as well as a word identification measure was given to both groups as a pre-test, and then the experimental group received the treatment in eighteen 30-minute sessions, in which the instructor taught skills to enhance students' orthographic knowledge. Meanwhile, the control group did not receive any specific treatment. Finally the post-test, which was the same as the pre-test was administered. Their scores were calculated through computer softwares. The results indicated that raising orthographic knowledge results in significant improvement in both word identification and reading comprehension. The findings of this study can benefit EFL learners in improving their reading comprehension skill.