Problem-Based Learning (PBL) is an effective instructional methodology used in higher learning. The purpose of this qualitative descriptive study was to explore what undergraduate engineering students perceive as barriers to the implementation of PBL in engineering courses at higher learning institutions in the Southwest United States. This research emerged from a gap that existed in the literature regarding the barriers students perceive in the online implementations of the PBL model in engineering coursework. This study was theoretically supported by the social constructivist learning theory and the PBL model. Three research questions explored how students describe the barriers faced in the overall implementation of the PBL as well as barriers specific to building content knowledge and collaboration. Purposive sampling was used to recruit 16 students in a common online engineering course offered at three higher learning institutions. Data were collected using 10 semi-structured conversational individual interviews and a focus group. Through thematic analysis, seven themes were identified: Instructor Communication and Involvement, Understanding Assignment Criteria and Instructor Expectations, Resource Availability and Functionality, Individual Student Motivation and Focus, Division of Workload and Responsibilities, Lack of Group Member Participation, and Poor Group Communication. The findings of the study suggest that students do face barriers during the online implementation of PBL, including access to their instructor, access to resources, personal motivation, and the participation of their peers. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]