The present field study investigates whether rater-ratee similarity in the Big Five personality factors influences peer ratings of contextual work behaviors. It overcomes problems that previous studies have had by using a polynomial regression analysis and by correcting the potential biases from nonindependence. Using more than 500 peer dyads, we found that rater-ratee similarity in Conscientiousness, but not in other dimensions, was positively associated with peer ratings even after controlling for interpersonal affect. These results suggest that the observed effect of personality similarity may reflect actual behavioral differences rather than biases due to interpersonal affect. Implications of the findings are discussed along with recommendations for future research.