After studying at the University of Athens, Kounellis travelled to Italy in 1956 to study at the Academy of Fine Arts in Rome under the Italian painter and poet Toti Scialoja. Jannis Kounellis produced his first paintings in the 1950s. Between 1959 and 1961 his works were inspired by letters, symbols and numbers, arranged on unusual materials such as wood and newsprint.

Influenced by Alberto Burri and Lucio Fontana, whose work offered an alternative to the expressionism of Informalism, Kounellis sought to bring painting to a brand-new territory. He was also inspired by the work of Jackson Pollock and Franz Kline, and by the earlier abstractions of Kazimir Malevich and Piet Mondrian. In 1963 Kounellis' work gradually became sculptural and added new elements into his paintings while exploring humble industrial materials such as iron, cotton, charcoal, wood, fire, jute, etc. Often linked to the world of work, he used these elements in contrasting ways according to their physical or semantic opposites. Through his works, the artist combined entirely opposing materials and notions: soft and hard, tar and steel, industrial and agrarian life, steel and jute. In 1967 he took part in the legendary exhibition Arte Povera-Im spazio curated by Germano Celant, officially joining the so-called povera movement. He replaced canvas with metal plates, which later became the main surface of his creations.

From the 1970s onwards, the artist took his work to a theatrical and musical dimension by designing several opera sets. Using a wide range of materials ranging from organic materials to minerals and items of animal origin (e.g. jute bags, coffee grounds, stones, crystals, linseed oil and even live animals), he delved into the intricate interplay between art and life, thus creating immersive experiences and truly dramatic stagings. In his later years, he intensified this kind of exploration, as he delved deeper into the realm of everyday materials while seamlessly adding furniture into his work it in monumental form.

Over the last five decades his works have been exhibited in venues such as the Tate Modern (London), the Neue Nationalgalerie (Berlin), the Museo d'Arte Contemporanea Donnaregina (Naples), the Tetriakov Gallery (Moscow), the Musée d'Art Moderne de la Ville de Paris, the Stedelijk Museum (Amsterdam), the Museo Nacional Reina Sofía (Madrid), the Galleria Nazionale d'Arte Moderna (Rome), MADRE (Naples) and Casa de San Agustín in the historic centre of Mexico City, among others. He also participated in eight Venice Biennials and three Documenta exhibitions in Kassel.

Pelaires has been working with Kounellis' works for the past 25 years, showing them in group exhibitions and, in particular, in two very special duo exhibitions: the first one —together with the artist Rebecca Horn— was held as part of the Gallery's 40th Anniversary. Entitled Aigüestortes, the project marked the beginning of a collaboration between the two artists, a collaboration that in 2011 took the form of a documentary by Pablo Bujosa Rodríguez and Pilar Rubí, currently available on the Filmin platform.

The second duo-exhibition project along with Antoni Tàpies, La infinitud de los soles, took place in Pelaires in 2022 and featured large-size works by the two artists.

A solo exhibition of Kounellis' works from 1990 to 2008 was held in 2024.