They were discovered after the Stena Line ferry from Cherbourg to Rosslare docked on Thursday afternoon.
The four adults, two teenagers and two children are all safe and well.
It is understood they were in what is known as a "curtain container" which had come from the French port.
Three ambulances attended the scene and all eight were medically assessed and brought to hospital for check-ups but none of them needed further treatment.
It is understood there was one family of six and two other adults and most, if not all, said they were Kurdish refugees.
They have been brought to Dublin where their claims for asylum will be processed.
Earlier this year, authorities at Rosslare Europort discovered 14 people hidden in the back of a lorry, which also arrived from France.
All 14 people, including one juvenile, were found inside a refrigerated trailer unit.
They did not need medical intervention either.
Eight people have been found in a container which arrived on a ferry into Rosslare Europort in County Wexford in the Republic of Ireland.