She worked for the Russian newspaper Novaya Gazeta and the Organized Crime and Corruption Reporting Project (OCCRP).

The topic of her doctoral thesis was "Small" newspaper Petrogradskiy Listok [ru; az; fr] in the period between the two revolutions of 1917.

[10][11] On 30 April 2020, it became known that Russian journalist Roman Anin and Olesya Shmagun are launching the Important Stories [ru] investigative journalism outlet.

[19][17][20] In 2017, Shmagun received the Pulitzer Prize for Explanatory Reporting as a member of the International Consortium of Investigative Journalists group.

[17][24][25] In 2021, Shmagun received the European Press Prize Investigative Reporting Award for an article "Kirill and Katya: Love, offshores, and administrative resources.