Wearing a light blue sweater and tan pants, Robinson spoke to confirm his identity and British nationality.
The victims were discovered in a truck container at Waterglade Industrial Park in Grays, by the River Thames, in Essex on October 23.
Another man has been arrested on suspicion of the manslaughter of 39 people found dead in a lorry in Essex.
Maurice Robinson, 25, appeared via video link at London's Central Criminal Court from the high-security Belmarsh prison, southeast London, and pleaded guilty to two of the 43 charges levelled against him.
Also on Monday, Maurice Robinson, the 25-year-old British truck driver who was the first to be arrested after the incident, admitted being part of an worldwide smuggling ring.
During the hearing before Mr Justice Edis, he admitted conspiracy to assist unlawful immigration between May 1 2018 and October 24 2019.
The charge read as "an act or series of acts which facilitated the commission of a breach of immigration law by various persons".
He did not enter pleas to 39 counts of manslaughter and conspiracy to traffic people. The youngest victim was 15 years old and the oldest was 44. He is charged with conspiracy to commit human trafficking offences between May 1 2018 and October 24 2019.
He also admitted to the acquisition of cash that came from criminal conduct.
"The Crown Prosecution Service has authorised 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 United Kingdom immigration law".
No trial date was set and Robinson is next due in court on December 13.
The 22 year-old appeared in a court in Dublin earlier this month charged with the deaths of the Vietnamese migrants. He was arrested in the early hours of Friday morning on the M40 in Beaconsfield, Buckinghamshire. Another accused, 23-year-old Christopher Kennedy, also of Northern Ireland, has been charged with human trafficking and was due to appear in court Monday.
Kennedy is charged with conspiracy to arrange or facilitate the travel of people with a view to exploitation and conspiracy to facilitate the commission of a breach of United Kingdom immigration law.