Insufficient pandemic preparedness and underfunding of human and economic resources have conditioned the response to COVID-19 in Spain. This underfunding has continued since the austerity measures introduced during the 2008 financial crisis. This study aims to understand the perceptions of healthcare staff in Spain on the relationship between the funding of the health system and its capacity to respond to the COVID-19 pandemic. To this end, we carried out a thematic content analysis, based on 79 online semi-structured interviews with healthcare staff across the regions most affected by the COVID-19 first wave. Participants reported a lack of material resources, which had compromised the capacity of the health system before the pandemic. The lack of human resources was to be addressed by staff reorganisation, such as reinforcing hospital units to the detriment of primary health care. Staff shortages continued straining the COVID-19 response, even after material scarcities were later partially alleviated. Personnel shortages need to be adequately addressed in order to adequately respond to future health crises.