In the transition to a more sustainable built environment over the last two decades, the “greening” of architecture as a popular approach has received widespread attention. However, there are still many open questions and contradictions regarding how to design with “nature” and contribute to sustainability. In addition, explorations of built examples are rare, and three-dimensional (3D) green spaces in buildings are often overlooked. Therefore, we introduce “green pockets” (3D green spaces) as a typology distinct from two-dimensional green roofs and walls/facades. We draw on a mixed-method approach to study two cases (Erasmus MC and Hotel Jakarta), comprising 12 semi-structured interviews with different stakeholders, design document analysis, and site observation. We develop a critical reflection (a framework) on the impacts of “green architecture” on sustainability from unpacked benefits and adopt a biophilic design framework to analyse designing with “nature” in architectural practice. These findings demonstrate that green pockets contribute to integrating multiple experiences of “nature” into buildings and developing sustainable architecture. Designing green pockets with visibility, accessibility, and spatial characteristics (e.g., prospect and refuge, organised complexity, peril, and mystery) of “nature” improves building quality. Furthermore, we provide design recommendations to advance green pocket designs and make suggestions for future research.