DPMC was formed as a result of a report that recommended establishing structures to provide two separate streams of advice to the Prime Minister.
These streams were a new government department to supply impartial, high quality advice and support to the Prime Minister and Cabinet (DPMC); and a Prime Minister's Private Office (which is not part of DPMC), to provide personal support and media services, and advice of a party political nature.
DPMC was established on 1 January 1990. Government House was included in the scope of the department in August 1990, after a review of the Governor-General’s support requirements. The External Assessments Bureau (now called the National Assessments Bureau) became part of DPMC on 1 July 1991.
The National Emergency Management Agency became a business unit within DPMC in April 2014.
The Canterbury Earthquake Recovery Authority (CERA) became a departmental agency within DPMC in February 2015. On 1 March 2016, to coincide with the wind down of CERA, a new business group - the Greater Christchurch Group - was formed to focus on the ongoing regeneration of Christchurch and support the transition of leadership from central government to local institutions. CERA was disestablished on 18 April 2016.
The Child Wellbeing and Poverty Reduction Group became a business unit within DPMC in February 2018. This group was established to support the Prime Minister as the MInister for Child Poverty Reduction and to support the development of New Zealand's first Wellbeing Strategy for children and young people.