Aarnio attended the School of Applied Arts in Helsinki and worked as a designer for Asko Oy from 1960-1962, leaving to start his own studio.
He began to experiment with plastics, vivid colors and organic forms. In 1963 he introduced the iconic Ball chair. The Pastil and the Bubble would follow in 1968. Because of their simple, geometric design, these pieces were often featured in films with a futuristic setting. Other well-known designs are the Tomato chair, the Screw table and the Puppy toy for children.
With a list of awards and honors that began in 1958, Aarnio continues to garner prizes, including the Compasso d'Oro Design award in 2007 for his Trioli chair and the Kaj Franck Design Prize in 2008.
His work is shown in museums around the world, including the Victoria and Albert Museum in London, MoMA in New York and Vitra Design Museum in Weil am Rhein.