Scaffolding has been shown to facilitate students' text comprehension and task performance. Yet less is known about the necessity of scaffolding for competent students reading unfamiliar content. To explore that question, we investigated the effects of two knowledge scaffolding techniques (i.e., mobilization and concept mapping) versus control on undergraduates' comprehension overall and by question type. The 118 undergraduates were randomly assigned to a condition and read a text about cellular biology. Results indicated a significant effect of scaffolding on students' comprehension after controlling for prior knowledge. Follow-up analyses for overall comprehension demonstrated that the concept mapping group outperformed the mobilization and control groups, and the mobilization group outperformed the control group. These results suggest that competent readers benefit from scaffolding when reading unfamiliar content.