Background Immediate Kangaroo Mother Care (iKMC) involves the initiation of skin-to-skin contact (SSC) between the mother (or an additional caregiver) and preterm and/or LBW infants within the first hours of birth, with exclusive breastfeeding. While KMC has traditionally been initiated after the infant stabilizes, immediate initiation of SSC has proven more effective in reducing neonatal mortality. However, despite its proven benefits, the adoption of immediate KMC remains a challenge. This study aims to develop and test an implementation model for integrating immediate KMC into the routine care of small and sick newborns in level 2 Special Newborn Care Units (SNCUs) in Bangladesh, Ethiopia, India, and Nigeria. Methods This multicountry implementation research study will develop and evaluate a scalable model for integrating iKMC into newborn care across six study sites in four countries. The study will involve developing and optimizing an implementation model using a mixed-methods design, combining both qualitative and quantitative approaches. Formative research will be conducted to identify barriers and facilitators to the effective implementation of iKMC, guiding the development of the initial model. The study will benefit from concurrent programme learning, using both qualitative insights and outcome measurements, to iteratively refine the model and ensure high-quality, widespread implementation of iKMC. Conclusion The study will provide insights into the effective integration of iKMC into existing health systems, addressing key challenges in low-resource settings. Findings will inform scalable strategies for widespread implementation, contributing to global efforts to enhance newborn care and reduce neonatal mortality.