Healthcare unit managers are pivotal to promote nurses' Perceived Organizational Support and hence to ensure nurses' health and well-being, as well as high-quality care. Despite this fact, there is a dearth of studies addressing how healthcare unit managers act and organize their work to promote nurses' Perceived Organizational Support and which working conditions enable them to do so. Through a mixed methods approach, comprising qualitative interviews and quantitative surveys among healthcare unit managers and nurses, this paper underscores that healthcare unit managers' availability to their nursing staff was essential for their ability to promote nurses' Perceived Organizational Support, and that responsive support from the care unit managers' superior management, administration, and managerial colleagues constituted enabling working conditions. Superior manager support strongly promoted the care unit manager's own Perceived Organizational Support, which, in turn, was positively correlated with nurses' organizational climate of Perceived Organizational Support.