Although natural playgrounds have originated from an intention to provide greater access to nature for children, these play spaces offer a designed and regulated space that diverges from other natural contexts. This study investigated the perceived and sociomaterially constructed role of nature in natural playgrounds by examining what people (i.e. playground designers and users) perceive and experience as natural within five natural playground sites in Calgary, Alberta. Drawing from interviews with playground developers, caregivers, and children that use the natural playground sites, this study describes what features are perceived as natural within the playgrounds, what shapes these forms of nature, and how these forms of nature may contribute to sustainable learning environments. This study found several opportunities and challenges surrounding sustainability, including the use of sustainable design within sites, the tension of sharing sites with non-human users, and the potential for further environmental education embedded within site design.