Severe bacterial infections fall among the leading causes of neonatal mortality (0-59 days) globally. One in every five neonates in Kenya will die due to these infections. This situation is aggravated by poor health care seeking behaviors by caregivers, poor supply chain management, low health provider staffing, low care giver and community health volunteer knowledge of PSBI presentation and management, dysfunctional referral pathways among others. The purpose of this study was the implementation of PSBI guidelines and generation of evidence aimed at addressing challenges in neonatal and young infant care in hard-to-reach resource-limited settings. The objective of this study was to demonstrate feasibility, acceptability, and sustainability of PSBI implementation within the revised IMNCI guidelines where referral is not feasible in selected counties in Kenya. The study employed implementation research where an initial formative context mapping and assessment was conducted with routine quarterly follow up assessments. Data collection entailed a capacity assessment in each of the four counties on various health system domains, facility audits in 12 purposively selected facilities to assess preparedness of facilities to manage PSBI, partner mapping to identify potential stakeholders for collaboration in each county, mapping of past, current and planned staff trainings, social costs analysis, Policy/stakeholder analysis, assessment of community/provider perceptions and practices regarding newborn care using in-depth interviews and focus group discussions. This was followed by six monthly case studies and narratives. Quantitative data was analyzed using independent T test and Pearson’s chi-square. Qualitative data was described using themes and narratives. Ethical clearance was sought from Mount Kenya University Institutional Scientific Ethics Review Committee. The data was reported using tables, graphs, pie charts and narratives. Dissemination of findings was through stakeholder forums, advocacy, local and international conferences, and publications in peer-reviewed journals. The health systems capacity assessment indicated average score of 70% across counties and service delivery domain where Turkana, Mombasa and Kilifi scored a green, but Bungoma scored amber of 65%. Only 29.2% of the facilities reported having a functional newborn unit/area for neonates from the facility assessment. Qualitative data alluded to several cultural contextual factors that predisposed young infants to infections. The data also revealed that most caregivers were able to identify danger signs of PSBI and roles of other household members were identified in line with influencing factors on care seeking behaviors. The interventions and decision support tools developed and tested to. facilitate integration of PSBI include a Job aid chart for health providers to aid in assessment and classification of sick young infants, informational pamphlets for caregivers and health providers, and a PSBI/IMNCI Assessment and Follow up tool for appropriate documentation of management of sick young infants. The findings on implementation research outcomes showed that indeed the PSBI guidelines are acceptable, adoptable, with clear indication of their fidelity, feasibility, and sustainability as public health interventions in low resource settings where referral for sick young infants is not feasible. Consideration of contextual variation, appropriate resource allocation, and training of health providers is necessary for sustainable integration of PSBI guidelines in Kenya’s healthcare system.