Maurice Robinson pleaded guilty at the Old Bailey to conspiring with others to assist illegal immigration between 1 May 2018 and 24 October 2019. The 25-year-old, from County Armagh, is accused of being part of a larger plot to bring people into the UK illegally. Mr Robinson was not asked to plead to 39 charges of manslaughter. The charges relate to the deaths of 39 Vietnamese people, including children, who were discovered in the back of a refrigerated lorry being driven by Mr Robinson in Grays on 23 October. Mr Robinson, who appeared via video-link from Belmarsh prison, also admitted acquiring criminal property - namely cash - between 1 May 2018 and 24 October 2019.
As well as the manslaughter charges, Mr Robinson is accused of conspiracy to commit human trafficking offences and transferring criminal property.
The defendant, of Laurel Drive, Craigavon, was remanded into custody until a further hearing on 13 December.
Eight women and 31 males, including two boys, aged 15, were among those who died.
Christopher Kennedy, 23, of County Armagh, Northern Ireland, has also been charged with human trafficking offences in relation to the deaths.
He also faces charges of conspiracy to arrange or facilitate the travel of people with a view to exploitation, and conspiracy to facilitate the commission of a breach of UK immigration law.
Three other people who were arrested on suspicion of manslaughter and conspiracy to traffic people have been released on bail.