The purpose of the present study was to determine whether noticing through input enhancement had any impact on the acquisition of English conditional sentences in Iranian EFL learners. Two intact classes with 26 female students in each were chosen. A proficiency test administered at the commencement of the study showed that the two groups were homogeneous in terms of their language proficiency. The standardized achievement pretest signified that the two groups were unfamiliar with the target structures prior to the treatment. The study employed a pre test post test non-equivalent groups design with two groups. The Enhanced group (Experimental group) received a set of materials in which the If-clauses were enhanced through enlargement and different combinations of bolding, italics, and underlining; whereas, the Unenhanced group (Control group) received the same set of texts with no enhancement on If-clauses. The independent t-test computed between the means of the two groups showed that there was a statistically significant difference between the performances of the two groups on the achievement post test. Besides, a retrospection questionnaire for operationalizing noticing was used after the treatment. The analysis of the students’ answers showed that input enhancement had helped the participants in the experimental group learn the conditional sentences.