BACKGROUND: Health system shocks are increasing. The COVID-19 pandemic resulted in global disruptions to health systems, including maternal and newborn healthcare seeking and provision. Yet evidence on mitigation strategies to protect newborn service delivery is limited. We sought to understand what mitigation strategies were employed to protect small and sick newborn care (SSNC) across 65 facilities Kenya, Malawi, Nigeria and Tanzania, implementing with the NEST360 Alliance, and if any could be maintained post-pandemic. METHODS: We used qualitative methods (in-depth interviews n=132, focus group discussions n=15) with purposively sampled neonatal health systems actors in Kenya, Malawi, Nigeria and Tanzania. Data were collected from September 2021 - August 2022. Topic guides were co-developed with key stakeholders and used to gain a detailed understanding of approaches to protect SSNC during the COVID-19 pandemic. Questions explored policy development, collaboration and investments, organisation of care, human resources, and technology and device innovations. Interviews were conducted by experienced qualitative researchers and data were collected until saturation was reached. Interviews were digitally recorded and transcribed verbatim. A common coding framework was developed, and data were coded via NVivo and analysed using a thematic framework approach. FINDINGS: We identified two pathways via which SSNC was strengthened. The first pathway, COVID-19 specific responses with secondary benefit to SSNC included: rapid policy development and adaptation, new and collaborative funding partnerships, improved oxygen systems, strengthened infection prevention and control practices. The second pathway, health system mitigation strategies during the pandemic, included: enhanced information systems, human resource adaptations, service delivery innovations, e.g., telemedicine, community engagement and more emphasis on planned preventive maintenance of devices. Chronic system weaknesses were also identified that limited the sustainability and institutionalisation of actions to protect SSNC. CONCLUSION: Innovations to protect SSNC in response to the COVID-19 pandemic should be maintained to support resilience and high-quality routine SSNC delivery. In particular, allocation of resources to sustain high quality and resilient care practices and address remaining gaps for SSNC is critical.