Krsnjavi studied painting in Munich and law in Vienna. After having completed his studies, he was travelling through Italy, where he painted mostly still lifes and landscapes, and copied Renaissance masters. His further work was strongly influenced by his meeting with J. J. Strossmayer in Rome, after which their mutual co-operation began on collecting famous masters' paintings for the future gallery. In 1875, he returned to Zagreb, when the building of the gallery began. As of 1877, he was a permanent resident of Zagreb, and the first professor at the Zagreb University Art History and Archeology Department. Because of his numerous public activities, he started neglecting painting, to which he returned only after WWI.

In 1878, he proposed the establishment of the Art Society, and, in 1882, that of Crafts School and Museum of Arts and Crafts. He was encouraging the development of decorative arts and popular creativity; he wrote the first professional art reviews in Croatia, put together the first holdings of Strossmayer's Gallery in Zagreb, and reorganized the Museum of Archeology. While he was Head of the Department of Theology and Education (1891-1896), he organized numerous exhibitions, as well as reorganized the schooling system. Owing to his efforts, many cultural institutions buildings were erected in Zagreb (the theatre, artistic ateliers). He provided scholarships and foreign training for a number of young artists (Racki, Ivekovic, Crncic), who then became quite renowned, introducing into Croatia's art new European developments.

He is also known as an art theoretician rather fond of aestheticising, historicism, and tradition.