Due to the ever-increasing leveraging of technology in learning and human performance, multimedia e-learning continues to see rapid adoption as an instructional method for both business and formal education environments. Cognitive load theory (CLT) and the cognitive theory of multimedia learning (CTML) provide prescriptive strategies to optimize the conditions of learning within the instructional material to manage the extraneous cognitive load to focus and manage the intrinsic and germane load, increasing the learner's ability to focus on the learning material. The power of an instructional designer to utilize these prescriptive strategies influences the effectiveness of the instructional material and its outcomes. This study focuses on instructional designers' decision-making and rationale regarding cognitive load in designing multimedia e-learning. It provides a necessary exploration into the rationale of how practicing instructional designers utilized learning theory in practice. The two theoretical frameworks for this study were the cognitive load theory and the cognitive theory of multimedia learning. A basic qualitative methodology was used whereby ten instructional designers from both business and educational environments participated in semi-structured interviews. Participants were chosen by their experience as an instructional designers of multimedia e-learning and their educational foundation. Interviews were conducted via Zoom, transcribed, validated, coded, and analyzed. Instructional designers predominantly use a small set of prescriptive strategies for managing cognitive load. Stakeholder engagement is crucial for the success of the design and development process. The findings reveal evaluation of learning outcomes and metrics of determining success are infrequently used to evaluate the effectiveness of managing cognitive load or determining learning success. [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/en-US/products/dissertations/individuals.shtml.]