The young child killed in an accident at the Hilden Brewery in Lisburn was a “little blond wonder”, a family friend said.
The incident happened at the Grand Street premises on Thursday.
Health and safety inspectors are investigating.
Councillor Pat Catney said the victim was “a force of nature”.
He added: “This little blond four-year-old wonder enchanted everyone who met him. He was part of the life here at the brewery and I know that the staff are also devastated at his death.”
Hilden Brewing Company was established by Ann and Seamus Scullion in 1981 in the courtyard of Hilden House, the former home of a linen-making family.
Its website said the independent microbrewery was the oldest of its kind on the island of Ireland.
A family statement said: “The Scullion-Hanna family is deeply upset by the death of a family member in an accident at the Hilden brewery today.
“The family would like to request privacy at this very difficult time.”
A PSNI spokesman said: “Police are currently in attendance at the sudden death of a child in commercial premises in the Grand Street area of Lisburn.”
A spokeswoman for the Health and Safety Executive in Northern Ireland (HSENI) said: “HSENI has been notified of the death of a young child at a commercial premises in the Lisburn area and is investigating the circumstances.
“We are unable to comment further at this stage except to offer our deepest sympathy to the family.”