He served as Under-Secretary of State for Foreign Affairs from 1883 to 1885 and again from 1905 to 1908, when he entered the cabinet as Chancellor of the Duchy of Lancaster under H. H. Asquith.

He was appointed Commissioner at Constantinople in 1880, overseeing the reorganisation of the European provinces of the Ottoman Empire under the Berlin Treaty of 1878.

He was in fact offered the position of Foreign Secretary (which for five years prior had been held by his brother Lord Lansdowne) should Sir Edward Grey refuse it (which he did not).

[9] He remained at the Foreign Office after H. H. Asquith became Prime Minister of the United Kingdom in April 1908 and was admitted to the Privy Council the same month.

However, a recurrence of his earlier illness forced him to resign the following year, marking the end of his political career.

Following Asquith's ascension to the premiership, Fitzmaurice was critical of what he saw as "the Liberals' aimless drift in domestic politics," although following his resignation he was (according to one study) "anxious to dispel rumours that his resignation was caused by a rift with Asquith or misgivings over Lloyd George's controversial 'People's Budget.

'"[1] Apart from his participation in national politics, Lord Fitzmaurice serve as Chairman of Wiltshire County Council from 1896 to 1906.