Post-neonatal mortality in New Zealand has decreased by 29% from 2009 to 2015, reaching 2.0 deaths per 1000 live births in 2015, down from 2.8/1000 in 2009. Since 2009, the New Zealand Ministry of Health has encouraged Safe Sleep policies for application in real world conditions. This paper puts the case for these policies as contributing causes for the improvement in post-perinatal mortality outcomes. The Ministry of Health has introduced five intervention strands at different times since 2009 that aim to promote infant sleep, constituting a Safe Sleep programme that is a multimethod public health intervention: 1. An end-stage strategy to break the impasse on mortality changes 2. A ‘blitz’ approach to sudden unexpected death in infancy (SUDI) education to achieve alignment, consistency and scale 3. An intervention focus on preventing accidental suffocation 4. The targeted supply of infant Safe Sleep devices (ISSDs) and Safe Sleep education 5. The development of Safe Sleep policies by District Health Boards. Over 2,600 health and community professionals each year for 4 years have participated in the SUDI education, equating to 1 participant per 23 live births. Safe Sleep leaflets have been distributed to families at more than twice the number of live births, and the number of Safe Sleep information cards designed for placement in hospital cots is approximately the number of babies born each year. In addition, over 16,500 ISSDs have been distributed to vulnerable infants. The fall since 2009 in post-neonatal mortality has been greatest for Māori and in regions with the most intensive programmes.