His career spanned Europe as he performed and/or sojourned in almost all major centres including Paris, Berlin, Warsaw, St Petersburg, Vienna, Stockholm, Basel, London, Dublin, amongst others.
It appears he was a pupil of Antonio Lolli and he was an acquaintance of Joseph Haydn, with whom he shared concert programmes in London.
It is "quite incredible," Tuksar has remarked, "that one of the leading musicians of 18th century Europe could have lived for 64 years without his name and surname ever being given anywhere, not even in his printed works, in their full and proper form."
Besides Jarnović, several variations in the rendition of his surname also occur: Jarnowick, Jarnovick, Jarnovichi, Jarnowicz, Garnovik, Giarnovicki, Giernovichi, Giornivichi.
The first and indisputably one of the most superior ones of the entire winter, was given on March 21 by Herr Giornowich ... one admires in the two violin concertos composed by him the beauty and novelty of the ideas just as much as the dexterity, power and extraordinary subtlety in the playing.
[11] It was published in Robert Smith's Sacred Music in Edinburgh in 1825, and may be an arrangement of a work of Jarnović made at that time.
[12] While in England, one of Jarnović’s several pupils was the young Mulatto prodigy George Bridgetower, for whom Beethoven subsequently composed the Kreutzer Sonata.
A bicentennial seminar and concert in honour of Jarnović was convened and hosted by the St Petersburg Union of Composers on 23–24 November 2004.