He resided successively in Florence and Paris, and travelled about Europe as private physician to Prince Jérôme Bonaparte, but when Pius IX was elected to the Holy See and began his reign with apparently Liberal and nationalist tendencies, Farini returned to Italy and was appointed secretary-general to G Recchi, the minister of the interior (March 1848).

But he held office for little more than a month, since like all the other Italian Liberals he disapproved of the Pius IX's change of front in refusing to allow his troops to fight against Austria, and resigned with the rest of the ministry on 29 April.

He resigned office on the proclamation of the republic after the flight of the pope to Gaeta in 1849, resumed it for a while when Pius returned to Rome with the protection of French arms, but when a reactionary and priestly policy was instituted, he went into exile and took up his residence at Turin.

As a member of the Sardinian parliament and as a journalist Farini was one of the staunchest supporters of Cavour, and strongly favoured the proposal that Piedmont should participate in the Crimean War, if indeed he was not actually the first to suggest that policy.

He negotiated an alliance with Parma, Romagna and Tuscany, when other provisional governments had been established, and entrusted the task of organizing an army for this central Italian league to General Fanti.

Annexation to Piedmont having been voted by plebiscite and the opposition of Napoleon III having been overcome, Farini returned to Turin, where the king conferred on him the order of the Annunziata and Cavour appointed him minister of the interior (June 1860), and subsequently viceroy of Naples; but he soon resigned because of ill-health.