After graduating from Lahti Polytechnic with a Bachelor's degree in graphic design in 2005, Pietari worked briefly as a graphic designer before moving to Barcelona where he pursued his career as a professional illustrator. His work has since appeared in The New York Times, the Guardian, Wired and Playboy, among other publications. Pietari has participated in several group exhibitions around the world, including the Now Showing Exhibition – Exploring the Lost “Art” of the Film Poster in London's Cosh Gallery in 2008. His work has been featured in the 3x3 Professional Illustration Annual and Print Magazine's European Design Annual in 2007 and in Gestalten's Naïve: Modernism and Folklore in Contemporary Graphic Design in 2009. His illustrations have been used in advertising, merchandise and apparel such as T-shirts, wallets and furniture. In 2010 Iittala released a series of dinnerware featuring Pietari's prints and in early 2011 the Finnish Post released a series of stamps with his designs.
The New York Times, New York Magazine, National Geographic Adventure, The Washington Post, The Los Angeles Times, Iittala, Paulig, The Guardian, Time Out, Nokia, American Airlines, British Airways, Runner's World, Best Life, Wired, Dwell, Portobello Books, Bloomberg Businessweek and Paste Magazine.