Named after the River Tamar in England, she is the fourth Batch 2 River-class vessel to be built[14] and is forward deployed long-term to the Indo-Pacific region with her sister ship HMS Spey.

On 6 November 2013 it was announced that the Royal Navy had signed an Agreement in Principle to build three new offshore patrol vessels, based on the River-class design, at a fixed price of £348 million including spares and support.

[25] Later in March, Tamar joined the French Navy's helicopter assault ship Dixmude and frigate La Fayette for exercises off Sri Lanka.

For these exercises, Tamar embarked divers and autonomous underwater vehicles to conduct mine countermeasures operations and monitor critical infrastructure.

[28][29] HMS Tamar went to the aid of HMNZS Manawanui when she ran aground off the south coast of Upolu island, Samoa, on 5 October 2024.