Background: Follow-up of sick young infants (SYIs) with signs of PSBI by community health workers (CHWs) can be useful in delivering simplified outpatient treatment. We describe how strengthening community-facility linkage increases fidelity, acceptability and sustainability of implementing WHO guideline on case management of PSBI when referral is not possible. Methods: The research adopted Hybrid II implementation research strategy using a mixed-methods evaluation across 39 primary care health facilities in Migori and Busia County. We trained 395 CHWs on two digital platforms CommCare and smart health to conduct home visits on days 2, 4, and 8, assess infants receiving treatment, encourage treatment adherence, and remind the caregiver to return for follow-up treatment at the facility. Results: Between August 2021 and May 2022, CHVs assessed 7622 newborns, 896(11.7%) were identified with PSBI danger signs and referred to primary health care facilities (PHCF) for treatment. CHWs completed all planned household visits, assessments, and referrals for SYIs, demonstrating feasibility and acceptability. Fidelity also improved for follow-ups: the proportion of SYIs with PSBI identified in the community, treated, and re-assessed on day 2 at PHCs increased over the same period (peaked at 94%). However, the proportion of PSBI cases followed up on days 4 and 8 remained low (at 29% and 26%, respectively) mainly due to caregivers’ reluctance to return to the facility for their baby’s re-assessment, citing cost and improvement of baby’s conditions. Conclusions: Digital interventions can potentially improve the identification, referral and tracking of PSBI cases by CHWs and linkage with PHCFs. Combining CHWs efforts with mobile digital strategy improves the acceptability and fidelity of implementing PSBI guidelines during COVID-19 and other similar emergencies.