The EIC engaged Princess Mary as an "extra ship" and she made four voyages for the company.

On 23 December Princess Mary was at the Cape of Good Hope; she arrived at Calcutta on 20 April.

Homeward bound, she was at Saugor on 3 May, reached the Cape on 21 August and St Helena on 17 November, and arrived at The Downs on 3 February 1799.

She was part of a convoy under escort by HMS Seahorse that also included General Stuart, Manship, Sarah Christiana, Northampton, Ann, Sovereign, Caledonia, Comet, Varuna, Carron, Elizabeth, Monarch, and Friendship.

[5] Princess Mary reached St Helena on 2 December and arrived at Calcutta on 21 March 1802.

[2] By the time Captain Grieve sailed again, war with France had resumed and he acquired a new letter of marque on 2 May 1803.

Princess Mary reached Rio de Janeiro on 16 September and arrived at Calcutta on 14 February.

She appears in Lloyd's Register for 1805 with B. Stout, master, M(oses) Agar, owner, and trade London–Jamaica.

[8] On 12 November a gale hit Halifax harbour, destroying or damaging many vessels, military and civilian.

Princess Mary was among the vessels gathering to sail back to England under convoy by HMS Poictiers, which rode out the gale.