Bush joined the New Zealand Police in 1978, working at both CIB and Uniform Policing. As he progressed through the ranks he was appointed to senior roles, including Liaison Officer for South East Asia. This position was held by Bush at the time of the 2004 Boxing Day tsunami. He was the first New Zealand official on the scene of this incident, arriving on Phuket to assist with relief. He was made a Member of the New Zealand Order of Merit (MNZM) for his relief work. He was awarded the New Zealand Special Service Medal (Asian Tsunami) recognising this work.
Upon appointment to the role of Commissioner of Police in 2014, Bush made several changes focused on operational models and culture. These included the introduction of a "Prevention First" operating model, where the primary focus of policing resources would be on crime prevention. Bush introduced additional core values of "Empathy" and "Valuing Diversity" in an effort to make cultural changes following the 2007 Commission of Inquiry into Police. Bush was reappointed to the role of commissioner in 2017 for a second term that will run until 2020.
In August 2014 Bush apologized on behalf of the police to the people of Ruatoki and Tuhoe following the actions of police in 2007 during the termination of the Operation Eight investigation into alleged terror activities. Tamati Kruger, acting as spokesman for Tuhoe, stated that the apology was well received by those present, however some Iwi had declined to take part.
In 2017 it was revealed that Bush had been convicted in 1983 of a drink driving offence while off duty. From 1991 onward, new rules were introduced where this conviction would have made Bush ineligible to join the police. It was revealed that Bush had followed the correct process that included disclosing this conviction to the State Services Commission prior to his appointment as a Deputy Commissioner.
Bush was a member of the State Services Commission panel that recommended the appointment of Wally Haumaha to a Deputy Commissioner role in June 2018. Bush was warned against this appointment by senior officers including Mike Clements, given the historic comments made by Haumaha in regards to the investigation of alleged offences against Louise Nicholas. A government inquiry into the appointment process by Mary Scholtens QC was announced to review the recruitment process, which led to Haumaha's appointment. The inquiry was welcomed by Bush.
- "Statement from Deputy Commissioner Operations, Mike Bush". New Zealand Police. 25 February 2014. Retrieved 15 March 2019.
- "New Year Honours List 2006". New Year Honours List 2006. Retrieved 31 October 2018.
- "New Zealand Special Service Medal (Asian Tsunami) – initial list of 163 eligible persons – 26 Dec 2005". Medals.nzdf.mil.nz. Retrieved 14 August 2018.
- "Formal Review of the New Zealand Police (Police)" (PDF). Ssc.govt.nz. Retrieved 31 October 2018.
- "Commissioner of Police". New Zealand Police. Retrieved 15 March 2019.
- "Police commissioner makes landmark apology to Tuhoe". Nzherald.co.nz. 13 August 2014. Retrieved 31 October 2018.
- "Police Commissioner Mike Bush admits drink driving conviction". Stuff.co.nz. Retrieved 31 October 2018.
- Savage, Phil Kitchin, Jared (22 July 2018). "Police Commissioner Mike Bush warned of Wally Haumaha's history, sources claim". Nzherald.co.nz. ISSN 1170-0777. Retrieved 14 August 2018.
- Herald, Jared Savage and Phil Kitchin for NZ. "Wally Haumaha phones witness to alleged bullying". Newstalkzb.co.nz. Retrieved 14 August 2018.
- "Commissioner of Police, Executive and District Commanders". Police.govt.nz. Retrieved 31 October 2018.
| Commissioner of Police
2 April 2014 – present