The function of the Marine Casualty Investigation Board (MCIB) is to examine and if necessary carry out investigations into all types of marine casualties to, or on board, Irish registered vessels worldwide and other vessels in Irish territorial waters and inland waterways.

The MCIB objective in investigating a marine casualty is to determine its circumstances and its causes with a view to making recommendations to the Minister for Transport and the commercial and recreational maritime community, for the avoidance of similar marine casualties in the future, thereby improving the safety of life at sea and on inland waterways.

The MCIB is a non-prosecutorial body which does not enforce laws or carry out prosecutions.  It is not the purpose of an investigation carried out by the MCIB to apportion blame or fault.

The legislative framework for the operation of the MCIB, the reporting and investigating of marine casualties and the powers of MCIB investigators is set out in the Merchant Shipping (Investigation of Marine Casualties) Act, 2000.

In carrying out its functions the MCIB complies with the provisions of the International Maritime Organisation's Casualty Investigation Code and EU Directive 2009/18/EC governing the investigation of accidents in the maritime transport sector.