IntroductionThere is growing evidence that parental participation in the care of small and sick newborns benefits both babies and parents. While studies have investigated the roles that mothers play in newborn units in high income contexts (HIC), there is little exploration of how contextual factors interplay to influence the ways in which mothers participate in the care of their small and sick newborn babies in very resource constrained settings such as those found in many countries in sub-Saharan Africa.MethodsEthnographic methods (observations, informal conversations and formal interviews) were used to collect data during 627 h of fieldwork between March 2017 and August 2018 in the neonatal units of one government and one faith-based hospital in Kenya. Data were analysed using a modified grounded theory approach.ResultsThere were marked differences between the hospitals in the participation by mothers in the care of their sick newborn babies. The timing and types of caring task that the mothers undertook were shaped by the structural, economic and social context of the hospitals. In the resource constrained government funded hospital, the immediate informal and unplanned delegation of care to mothers was routine. In the faith-based hospital mothers were initially separated from their babies and introduced to bathing and diaper change tasks slowly under the close supervision of nurses. In both hospitals appropriate breast-feeding support was lacking, and the needs of the mothers were largely ignored.ConclusionIn highly resource constrained hospitals with low nurse to baby ratios, mothers are required to provide primary and some specialised care to their sick newborns with little information or support on how undertake the necessary tasks. In better resourced hospital settings, most caring tasks are initially performed by nurses leaving mothers feeling powerless and worried about their capacity to care for their babies after discharge. Interventions need to focus on how to better equip hospitals and nurses to support mothers in caring for their sick newborns, promoting family centred care.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12884-023-05686-3.