Turning to politics, he was elected a member of Dublin Corporation representing the Guild of Merchants, and was popular for his denunciation of municipal corruption and his proposal of a boycott of English goods in Ireland in retaliation for the restrictions imposed by the Westminster government on Irish commerce.

He was one of the most conspicuous members of the small revolutionary party, chiefly of the shopkeeper class, that formed a permanent committee in June 1784 to agitate for reform, and called a convention of delegates from all parts of Ireland.

This was treated by the House of Commons as a breach of a Member's privilege, and a Speaker's warrant was issued for his arrest, which he managed to elude until its validity expired on the prorogation of Parliament.

In the following year, Napper Tandy took a leading part in organising a new military association in Ireland modelled after the French National Guards; they professed republican principles, and on their uniform, the cap of liberty instead of the crown surmounted the Irish harp.

In February of that year, he went to Paris, where a number of Irish refugees, the most prominent of whom was Wolfe Tone, were assembled, planning rebellion in Ireland to be supported by a French invasion, but quarrelling among themselves over tactics.

[3][4] Tandy accepted the offer of a corvette, (later captured by the British and renamed Anacreon), from the French government and sailed from Dunkirk accompanied by a few United Irishmen, a small force of men and a considerable quantity of arms and ammunition for distribution in Ireland.

Tandy took possession of the village of Rutland, where he hoisted an Irish flag and issued a proclamation; but learning of the defeat of Humbert's expedition, and that Connaught was now subdued, the futility of the enterprise was soon apparent.

[8][9] Notwithstanding his vices and his lack of all solid capacity, there is no reason to suppose that Napper Tandy was dishonest or insincere; and the manner in which his name was introduced in the well-known ballad "The Wearing of the Green" proves that he succeeded in impressing the popular imagination of the rebel party in Ireland.

In France, where his release was regarded as a French diplomatic victory, he was received, in March 1802, as a person of distinction;[3] and when he died on 24 August 1803 in Bordeaux, his funeral "was attended by the whole army in the district and an immense concourse of citizens."