To complete any academic tasks using information from the Internet, undergraduate students first have to select the appropriate sources. However, the types of justifications that undergraduates provide for source selection and how these justifications may be impacted by task characteristics have been underexamined. This study explored undergraduates' reported justifications for source selection when responding to questions in a digital academic context. Participants were first asked to answer two questions, one discrete and one open-ended, using an online library of eight sources varying in type and reliability. Subsequently, a guided retrospective interview was used to elicit undergraduates' justifications for source selection. Source selection decisions were coded as epistemic (e.g., concerned with reliability or credibility) or nonepistemic (e.g., concerned with relevance or accessibility). Undergraduate students' justifications were significantly more likely to be nonepistemic than epistemic. Further, the reasons for selection offered differed when participants responded to the discrete versus open-ended question, to a limited extent. Epistemic justifications for source selection were related to a number of outcome measures, while nonepistemic justifications were not. Findings are discussed in reference to research and practice pertaining to undergraduates' multiple source use and task design.