Intellectual engagement is an absorbing, creatively energized focus resulting in a deep personal commitment to exploration, investigation, problem-solving and inquiry over a sustained period of time. In this article, the authors argue that participatory learning environments with a focus on knowledge building offer clear learning benefits to students and teachers. They describe three inquiry projects that were designed to promote intellectual engagement through knowledge building in participatory learning environments. In each of these projects, socially and digitally connected learners sought out complex issues and problems, worked hard to understand and solve them while collaborating with peers, and engaged with audiences and expertise beyond the classroom. Finally, the authors observe that strong task design and ongoing, continual assessment of the learning taking place were essential to ensuring a rich learner experience. (Contains 6 endnotes.)