This paper examines the effectiveness of adding an online component to the general chemistry laboratory in which students view prelaboratory instructional materials through online videos prior to completing general chemistry laboratory activities. Using a quasi-experimental design, we compared the performance of 1089 general chemistry students who viewed online prelaboratory videos for two laboratory activities and attended face-to-face prelaboratory lectures for two additional laboratory activities. Students were assessed on their understanding of the rationale for specific laboratory procedures, their efficiency at completing each activity in the allotted time, and their help-seeking behavior during laboratory sessions. Students were more efficient and demonstrated a greater understanding of the rationale for procedures for the two laboratory activities that used online prelaboratory videos than those that used prelaboratory lectures. No differences were observed in help-seeking behavior between the two conditions. These results suggest that online prelecture videos have significant potential for improving student learning in the general chemistry laboratory and for reducing demand on institutional resources for associated courses.