Following a two-decade-plus career in Finnish movies, Pääkkönen's international breakthrough role came in 2015 in the historical drama television series Vikings (2016–2018; 2020) as Halfdan the Black.

According to a calculation published by Finnish tabloid Ilta-Sanomat, Pääkkönen is "the most profitable film actor in Finland"[9] for having starred in numerous box office hits during his career.

Other of Pääkkönen's commercial and critical successes include Frozen Land (2005), Matti: Hell Is for Heroes (2006), Lapland Odyssey (2010) and Heart of a Lion (2013).

He has earned international praise from film critic Michael Giltz from the Huffington Post, who called the actor "handsome and compelling"[11] in his role in Lapland Odyssey.

Film critic Leslie Felperin from Variety named Pääkkönen a "rising thesp, showing impressive range" in his starring role in Matti.

[14] Pääkkönen co-starred as a KKK member in Spike Lee's drama BlacKkKlansman, which premiered at the Cannes Film Festival and was released on 10 August 2018.