The study investigates peer rating, one of the most commonly used sources of performance rating other than those of supervisors. On the whole, both field and laboratory studies indicate that peer assessment is a valid and reliable evaluation procedure, but on average, peer rating is not usually accurate. The aim of the investigation is to explore the relationship of beliefs and attitude about the performance appraisal system as well as a dispositional characteristic as self-monitoring with rating behavior. In particular, the study tests whether the relationship between rating context variables-appraisal self efficacy and appraisal validity- and rating behavior depends in part on the personality of the rater. Data from 445 undergraduate students are analyzed for hypotheses testing. The study finds evidences that the high on appraisal self efficacy and appraisal validity are more likely to affect discriminating rating tendency and to reduce rating level. Results also show that self-monitoring make the moderating effects between contextual factors and rating behaviors. Some implications, future research directions, and limitations are discussed.