BackgroundReducing the burden of neonatal sepsis requires timely identification and initiation of suitable antibiotic treatment in primary health care (PHC) settings. Countries are encouraged to adopt simplified antibiotic regimens at the PHC level for treating sick young infants (SYI) with signs of possible serious bacterial infection (PSBI). As countries implement PSBI guidelines, more lessons on effective implementation strategies and outcome measurements are needed. We document pragmatic approaches used to design, measure and report implementation strategies and outcomes while adopting PSBI guidelines in Kenya.MethodsWe designed implementation research using longitudinal mixed methods embedded in a continuous regular systematic learning and adoption of evidence in the PHC context. We synthesized formative data to co-create with stakeholders, implementation strategies to incorporate PSBI guidelines into routine service delivery for SYIs. This was followed by quarterly monitoring for learning and feedback on the effect of implementation strategies, documented lessons learned and tracked implementation outcomes. We collected endline data to measure the overall effect on service level outcomes.ResultsOur findings show that characterizing implementation strategies and linking them with implementation outcomes, helps illustrate the pathway between the implementation process and outcomes. Although we have demonstrated that it is feasible to implement PSBI in PHC, effective investment in continuous capacity strengthening of providers through blended approaches, efficient use of available human resources, and improving the efficiency of service areas for managing SYIs optimizes timely identification and management of SYI. Sustained provision of commodities for management of SYI facilitates increased uptake of services. Strengthening facility-community linkages supports adherence to scheduled visits. Enhancing the caregiver’s preparedness during postnatal contacts in the community or facility will facilitate the effective completion of treatment.ConclusionCareful design, and definition of terms related to the measurement of implementation outcomes and strategies enable ease of interpretation of findings. Using the taxonomy of implementation outcomes help frame the measurement process and provides empirical evidence in a structured way to demonstrate causal relationships between implementation strategies and outcomes. Using this approach, we have illustrated that the implementation of simplified antibiotic regimens for treating SYIs with PSBI in PHC settings is feasible in Kenya.