This study investigates the effect of Jordanian Eleventh grade students' self-assessment on their performance in reading in English. The sample of the study consisted of an experimental group and a control group; each group consisted of two eleventh grade sections (67 male and 69 female students). A reading test was developed and its validity and reliability were established. To collect data about the students' progress, I used student self-assessment through one-minute papers and rating-scale sheets. The findings of the study revealed that student self-assessment had positive effect on their performance in reading in English. In light of the findings, it is recommended that students be trained on how to use self-assessment, and that instructors become aware of the positive effect of student self-assessment on their performance in reading. (Contains 5 tables, 1 figure and 1 note.)