Play provides a foundation for human learning because people have an opportunity to experiment through play and learn in a safe environment. Although play is more free-form, expressive, and improvisational, serious play is more structured, rule-bound with a "serious" purpose (Deterding, Dixon, Khaled, & Nacke, 2011). Studies also show that learning engagement is a key determinant of learning effectiveness and learning outcomes (Clark, 1994; Liaw, Huang, & Chen, 2007; Hu & Hui, 2012). Since its official launch to the market in 2002, LEGO® SERIOUS PLAY® (LSP) has been widely used to engage and influence learners in learning (Gauntlett, 2007; Heracleous & Jacobs, 2011; Kristiansen & Rasmussen, 2014). Knowing what constructs make up learning engagement in LSP will support those who use LSP as a medium to help its learners achieve the intended learning outcomes. The results of this study could also be generalized to the larger realm of learning engagement. This phenomenographic research presents empirical evidence of what constructs of learning engagement affect adult learning using LSP methodology. The findings suggest seven constructs of learning engagement in LSP, which are interwoven with each other. They are organized into three principal areas: Motivational Constructs (Flow, Safety), Socio-materiality Constructs (Materiality, Interaction), Meaningfulness Constructs (Reflection, Reinforcement), all of which are mediated by the Stretching Construct. These constructs suggest four ways to enhance learning engagement using LSP methodology for adult learners which are discussed in the dissertation. The study further reveals learning engagement in LSP is not something enacted by "what" LSP is but about "how" LSP is enacted. Through appropriate stretching in the interplay of instructional design and facilitation, playing and learning can create a positive spiral effect of the flow state to engage adult learning. [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.]