Arthur Hart Guinness was the second son of Arthur Guinness and his wife Olivia Whitmore, and was born at their home at Beaumont House (now a part of Beaumont Hospital, Dublin). He attended White's Academy in Grafton Street, Dublin, (now the site of Bewley's). Arthur started working for his father at the St James's Gate brewery from the 1780s. In 1790 his father, then aged 65, commented in a letter that the expansion of his brewery was partly due to his help:
