In Zanzibar, the United Kingdom’s engagement was defined both by commerce and a desire to end the Indian Ocean slave trade.

[2] In 1919, the British gained control of most of Tanganyikan territory, following a League of Nations mandate that ended the period of German colonial administration that had started in 1884.

Tanzania broke off relations with the United Kingdom between December 1965 and July 1968, in response to British policy towards Rhodesia's Unilateral Declaration of Independence.

In 2021 the United Kingdom ranked fourth for foreign direct investment into Tanzania behind the Cayman Islands, China and Canada.

The only British firm listed on the Dar es Salaam Stock Exchange was Acacia Mining before its delisting on 18 November 2019.