He began his musical studies at an early age of three, playing the cello and singing as a boy soprano soloist in the boys' choir of Helsinki Cathedral's Cantores Minores, with whom he still regularly cooperates as a concert soloist.

He began his professional studies at the Helsinki Conservatory, followed by the Metropolia University of Applied Sciences in Helsinki and the Stockholm University of the Arts. He received important artistic impulses by singers such as Heikki Orama, Tommi Hakala, Tuomas Katajala, Neil Shicoff, John Norris, Andrew Watts and Gregory Lamar. His concert repertoire includes works of baroque and renaissance music, lied and oratorio. He works with institutions such as the Jyväskylä Sinfonia, the Helsinki Baroque Orchestra, the Tapiola Sinfonietta, and the Turku Philharmonic Orchestra. In 2021, Johan Krogius won the Timo Mustakallio singing competition and was awarded 1st place at the Helsinki Lied competition in the same year.

As an opera singer, Johan's lyrical tenor could be heard in roles such as Jaquino Fidelio and Pong Turandot in Helsinki, 1st Man in Joonas Kokkonen's The Last Temptations at Opera Jyväskylä, Don Ottavio Don Giovanni at the Finnish National Opera in Helsinki, and as Tamino Die Zauberflöte at Opera Tampere as well as, most recently, the Savonlinna Opera Festival.

As of season 2022/23 Johan Krogius is a member of the International Opera Studio at Staatsoper Unter den Linden Berlin, where he was already on stage as Haushofmeister bei Faninal Der Rosenkavalier, Trojaner Idomeneo, Erster Priester and Erster Geharnischter Die Zauberflöte, Parpignol La Bohème and Borsa Rigoletto, among others.

In season 2023/24 at Berlin's State Opera his roles included Leukippos in Strauss' Daphne, Tamino Die Zauberflöte, Ein Wirt and Haushofmeister bei Faninal Der Rosenkavalier, and Streschnew in Mussorgky's Khovanshchina.

In summer 2024 Johan returned to the Savonlinna Opera Festival in the roles of Don Ottavio Don Giovanni and Ismaele Nabucco.

In the upcoming season 2024/25 his projects include Khovanshchina Kuska on a concert tour with the Finnish Radio Symphony Orchestra and Esa-Pekka Salonen, Joonas Kokkonen's opera The Last Temptations at Tampere Opera, Mozart's Requiem at the Berlin Philharmonie, and Beethoven's Symphony no 9 at the Berliner Dom.

At Staatsoper Unter den Linden he will make his role debuts as Tybalt in Roméo et Juliette, Erscheinung eines Jünglings Die Frau ohne Schatten and Erster Gralsritter in Parsifal, as well as singWirt in Der Rosenkavalier.