The evaluation of gardens in healthcare facilities through post-occupancy evaluations (POE) is essential for research and evidence-based design. Access to green spaces in healthcare facilities has been shown to improve physical, emotional, and mental outcomes for patients, visitors, and staff, and can be considered part of a holistic approach to health. By applying systematic, valid methods to assess these spaces, we can standardize research into the design of gardens and other natural spaces in healthcare facilities. Results from this, and similar garden evaluations can also be used as guides for future design and research into the policy, programming, and design to optimize user health and well-being outcomes. This study adapted the Healthcare Garden Evaluation Toolkit (H-GET) for pediatric use in order to evaluate a rooftop garden at a pediatric healthcare facility. The H-GET is a mixed methods toolkit consisting of a garden audit tool (GATE), behavior mapping observation, staff survey, and stakeholder interviews, and allows for the collection and analysis of both quantitative and qualitative data. Results of this evaluation suggested that high garden quality, as measured by the GATE audit and staff surveys, is related to high garden usage, and staff believe that the garden was good for mental and physical health. Barriers to use included visibility, accessibility, and insufficient shading and seating. Recommendations for design, policy, and programming in the gardens highlight opportunities for improvements in this and future gardens at healthcare facilities to increase usage and proliferate the multitude of benefits that access to nature can provide.