Prior research has found strong and persistent effects of instructor first impressions on student evaluations. Because these studies look at real classroom lessons, this finding fits two different interpretations: (1) first impressions may color student experience of instruction regardless of lesson quality, or (2) first impressions may provide valid evidence for instructional quality. By using scripted lessons, we experimentally investigated how first impression and instruction quality related to learning and evaluation of instruction among college students. Results from two studies indicate that quality of instruction is the strongest determinant of student factual and conceptual learning, but that both instructional quality and first impressions affect evaluations of the instructor. First impressions matter, but our findings suggest that lesson quality matters more.