There is little emphasis given by the discipline of ergonomics to hospital architecture in Brazil. As such, this paper presents a case study of an ergonomic evaluation done in the Brasilia Children’s Hospital. The research focused on the spatial quality and user satisfaction through an ergonomic standpoint. It analyzed the pediatric oncology therapy area, focusing on chemotherapy treatment. Therefore, the intent here is to increase the scarce existing material on the architecture literature dedicated to the study of this spatial typology. The case study showed that ambiance is key in creating a sense of well-being, hospitality, and comfort to users. It contributed to a didactic interaction with patients, breaking the usual concept of sobriety and sterility of a hospital. This promoted the interaction between different actors, which avoided the habitual isolation of a child in new spaces and discomforts with certain therapeutic practices. As such, this paper discusses evaluation and proposal – under the focus of Ergonomics applied to the built environment – of a children’s day hospital for cancer treatment.