Architectural design is a knowledge-intensive activity; however, students frequently lack sufficient knowledge when they practice design. Collaborative learning can supplement the students' insufficient expertise. Successful collaborative learning relies on knowledge sharing between students. This implies that the peers are a considerable design knowledge source for the students. However, students are involved in grade competition. Students may not be willing to share because knowledge is a critical resource for students' performance. The web technology has been used to facilitate knowledge exchange among students; nevertheless, the convenience of technology may tempt free riding behavior and impede the development of a knowledge sharing culture. The purpose of this exploratory study is to probe whether the peers and a web forum are the students' primary knowledge source by investigating students' knowledge sources during the design process. The results demonstrated that (1) studio-mates were a primary design knowledge source for the students, (2) the ill-defined nature of design problems may be the main contributing factor encouraging knowledge sharing behavior, (3) the shared web forum was not a primary knowledge source for the students and did not have a significant influence on the knowledge sharing culture, and (4) we can estimate the knowledge sharing culture in a design studio through investigating students' knowledge sources. Furthermore, several additional findings and implications are elaborated.