Police Ombudsman Al Hutchinson is appointing a former senior civil servant as interim chief executive as he prepares to return to Canada at the end of March.
Colin Lewis will stand in as head for six months until a new team at the Belfast office is in place.
Mr Hutchinson, who faced widespread political pressure to step down after controversy at his office, will return home after taking leave in February.
Married father-of-three Mr Lewis has been working within the Department of Enterprise, Trade and Investment since 2009. He formerly worked for KPMG chartered accountants.
Mr Hutchinson said: "I am pleased that someone with Colin's experience in both the private and government sectors has accepted the challenge of serving Northern Ireland in this important office. Colin's knowledge and senior level leadership, supported by a very able Police Ombudsman team, will add valuable continuity and independence during this challenging period of change to the office of the Police Ombudsman."
Mr Hutchinson announced his intention to quit following a report which identified significant failings in the work of his office.
Former chief executive Sam Pollock resigned last March and said he was unhappy with the approach taken in controversial cases involving informers and also claimed the independence of the office had been diminished.
A report published in September by the Criminal Justice Inspectorate concluded that there "has been a lowering of the operational independence" of the office in the way it conducts investigations into historical cases. The inspectors said the ombudsman should suspend historical investigations.
Inspectors examined several historical cases in which the ombudsman was asked to investigate allegations that the RUC had failed to properly investigate murders during the Troubles. They included the UVF bombing of McGurk's bar in north Belfast in 1971, in which 15 people died.
The report describes the investigative processes as flawed and says inspectors found that a number of reports - including the one on McGurk's - had been altered before publication to reduce criticism of the police, with no explanation.