Hagelberg has been widely published in various anthologies all over Europe and in the USA. Several of his books have come out in France: Holmenkollen (L’Association, 2002), Le Sultan De Vénus et autres möelles d’invertébrés, (L’Association, 2003), Kekkonen, (L’Association, 2007), Hard West, (L’Association, 2009), Le 14e jour du Mois (Hoochie Coochie, 2014), and Silvia Regina (L’Association, 2015). Other books of his published in France are Universal Pictures, Mr. Mokamat, Zombie Justice, and Unfinished/abandoned from Le Dernier Cri; and The Sinful Ways of Simpli City from Chacal Puant. In 2012, he started a monthly comic book series, Läskimooses (B.E.M. #20), which came out as a 1,480-page book in 2021.

His works have been displayed in various group exhibitions. Apart from comics, Hagelberg has written a libretto for an opera based on his comics in association with Karla Loppi, Marsin mestarilaulajat (Mastersingers of Mars, 2000), composed by Kimmo Hakola. Since 1998, he has taught comics at the University of Art and Design. He lives and works in Helsinki.