Coming across clowns in a hospital is never a mundane experience. If medical teams seem to be getting used to the hullaballo they provoke, most families claim they get a feeling of being transported elsewhere. How do clowns work with hospital ambiances in all their varieties? Drawing on data collected during fieldwork in two different hospitals, where clowns from Le Rire Médecin perform twice a week, I will show how ambiances are created through a series of in situ interactions with the hospital space as well as with the numerous “actors” who inhabit it.