This purpose of this pre-post, quasi-experimental evaluation was to explore the impact of grading rubric use on student academic performance. Cross-sectional data were derived from 80 undergraduates enrolled in an elective course at a research university during spring and fall 2009. The control group (n = 41), who completed the course's Assignment #2 without a grading rubric, scored significantly lower, on average, than the treatment group (n = 39), who completed the same assignment, but with access to a grading rubric. The grading rubric constituted an important predictor of assignment performance, the magnitude of which was stronger than college year, major, pre-test score, and gender. Suggestions are provided for future research. (Contains 1 figure and 5 tables.)