Experts have advocated anonymous grading as a means of eliminating actual or perceived evaluator bias in subjective student assessment. The utility of anonymity in assessment rests on whether information derived from student identity can unduly influence evaluation. The halo effect provides a conceptual background for why a bias might occur. In the present study examining the halo effect, psychology faculty members and teaching assistants were randomly assigned to grade a student giving a poor oral presentation or the same student giving a good oral presentation. All graders then assessed an unrelated piece of written work by the student. As hypothesized, the graders assigned significantly higher scores to written work following the better oral presentation. The results provide strong evidence of a halo effect in that prior experience with a student biased the grading of written work completed by the student. The findings suggest the need to keep students anonymous when feasible in order to minimize the risk of unfair grading.