INTRODUCTION: Appropriate demand for, and supply of, high quality essential neonatal care is key to improving newborn survival but evaluating such provision has received limited attention in low- and middle-income countries. Moreover, specific local data are needed to support healthcare planning for this vulnerable population. METHODS: We conducted health facility assessments between July 2015-April 2016, with retrospective review of admission events between 1st July 2014 and 30th June 2015, and used estimates of population-based incidence of neonatal conditions in Nairobi to explore access and evaluate readiness of public, private not-for-profit (mission), and private-for-profit (private) sector facilities providing 24/7 inpatient neonatal care in Nairobi City County. RESULTS: In total, 33 (4 public, 6 mission, and 23 private) facilities providing 24/7 inpatient neonatal care in Nairobi City County were identified, 31 were studied in detail. Four public sector facilities, including the only three facilities in which services were free, accounted for 71% (8,630/12,202) of all neonatal admissions. Large facilities (>900 annual admissions) with adequate infrastructure tended to have high bed occupancy (over 100% in two facilities), high mortality (15%), and high patient to nurse ratios (7-15 patients per nurse). Twenty-one smaller, predominantly private, facilities were judged insufficiently resourced to provide adequate care. In many of these, nurses provided newborn and maternity care simultaneously using resources shared across settings, newborn care experience was likely to be limited (<50 cases per year), there was often no resident clinician, and sick babies were often referred onwards. Results suggest 44% (9,764/21,966) of Nairobi's small and sick newborns may not access any of the identified facilities and a further 9% (2,026/21,966) access facilities judged to be inadequately equipped. CONCLUSION: Over 50% of Nairobi's sick newborns may not access a facility with adequate resources to provide essential care. A very high proportion of care accessed is provided by four public and one low cost mission facility; these face major challenges of high patient acuity (high mortality), high patient to nurse ratios, and often overcrowding. Reducing high neonatal mortality in this urban, predominantly poor, population will require effective long-term, multi-sectoral planning and investment.