From 1797 she made four voyages as a slave ship in the triangular trade in enslaved people.

1st voyage transporting enslaved people (1797–1798): Captain John Clare sailed from Liverpool on 5 May 1797.

[3] 2nd voyage transporting enslaved people (1798–1800): Captain William Neal acquired a letter of marque on 10 August 1798.

[6] She sailed for Liverpool on 24 October with Thomas Waring as master and arrived there on 24 January 1800.

[5] 3rd voyage transporting enslaved people (1800–1801): Captain Samuel Helmsley acquired a letter of marque on 28 April 1800.

[7] On 12 March 1801, HMS Leda recaptured the enslaving ship Bolton, a 20-gun letter of marque that had sailed from Demerara for Liverpool some six weeks previously in company with Union and Dart.

These two vessels were also enslaving ships and letters of marque, all carrying valuable cargoes of sugar, coffee, indigo and cotton.

[8] Lloyd's List reported in June 1802 that Dart, Helmsley, master, had put into Barbados on her way from Demerara to London.