The article is devoted to the analysis of a source stored in the Archive of Foreign Policy of the Russian Empire – the reports of Vasily Valentinovich Musin-Pushkin-Bruce, a Russian diplomat at the court of the Neapolitan king Ferdinand IV. Fleeing from the French troops approaching Naples, he went to Sicily after the royal court. From there, from the city of Palermo, Musin-Pushkin-Bruce wrote reports to the Russian emperor Paul I, in which he outlined the events taking place in southern Italy after the French captured Naples and established the Neapolitan Republic there in January 1799. This source was used by Russian researcher Galina Alekseevna Sibireva, who published the monograph “The Kingdom of Naples and Russia in the Last Quarter of the 18th Century” in 1981. However, due to the fact that Sibireva's focus was on the development of economic, political and cultural ties between the Russian Empire and the Kingdom of Naples, a number of events remained outside her interests, information about which we can glean from this source. The Musin-Pushkin-Bryus reports allow us to reveal such aspects as the social composition of the republican and anti-revolutionary forces, the importance of religion in the life of Neapolitan society and the role it played in the resistance of the population of Southern Italy to the republicans, and also to trace who organized the unrest in Sicily, which became an echo of the Neapolitan events.