He studied at the Zagreb Academy of Fine Arts, and subsequently moved to France, where he spent the rest of his life and was known as Lorris Junec.
[2] In 1909, Junek enrolled in Zagreb's Kaptol Jesuit Seminary, where he learned music and sang as a chorister in the cathedral choir.
According to multiple written sources (Babić, Hegedušić, Horvat, Zidić), and a letter exchanged between Junek and the Baroness Vera Nikolić Podrinska, his studies were funded by his birth father, Hugo Mihalović.
[2] Towards the end of his studies, Junek visited Paris on a trip funded by the Baroness Vera Nikolić Podrinska, and fell in love with the city.
Returning to Zagreb with a series of portraits (still lives and nude studies), he opened his first solo exhibition at the Salon Anton Ulrich, where he showed 21 oil paintings.
[2] As Junek gradually disapproved of a collective, communal approach to artistic expression, and was relatively uninterested in political engagement, his affinities with the Zemlja group diminished over time.
Around the same time, Junek was selected for an exhibition in Belgrade, and showed his works in the Croatian section of the Cvijeta Zuzorić Art Pavilion.
[citation needed] In 1933, Junek painted the portrait of his daughter Eveline à la mandoline and Glaïeuls.
He exhibited 73 works, most of his Parisian œuvre over the previous ten years, which proved largely influential on Croatian painting.
Persuaded by his friends, he showed three oils to Berthe Weill, an art dealer who owned a successful gallery and regularly exhibited Cézanne, Picasso, Matisse, and Raoul Dufy.
In this gallery, Dufy spotted Junek's Glaïeuls, and invited him to his studio, where he was shown Eveline à la mandoline, and a few watercolours.
In his works Le Dessinateur and Maternité Port Royal, he does not deny reality, but rather seeks to represent it in the form of an enigma that the beholder must resolve.
Grgo Gamulin sees in Le Dessinateur the origins of Junek's interest in abstraction, and the birth of a "lyrical, 'tachist' style of painting in France".
At an exhibition, he befriended Jean René Bazaine, with whom he shared his vision of painting as inextricably indebted to the art of Poussin.
In 1951, he travelled to Chartres to study the cathedral and the famous stained-glass windows, and became passionate about French medieval painters, especially Jean Fouquet.
In 1968, Junek befriended the Swiss writer and critic Georges Borgeaud, who took a liking to his works, and with the help of Bazaine, assisted the painter in preparing for his first solo exhibition in Paris, at the gallery Pierre Domac.
Between 1975 and 1980, Junek travelled every year to Italy and visited 'art capitals' such as Milan, Florence, Venice, Padua, Ravenna, and Genoa.
He also exhibited at the 1991 Exposition collective des maîtres de la peinture française contemporaine (also known as Une rencontre exceptionnelle) in Rosny-sur-Seine.
Josip Vaništa, Georges Borgeaud, Daniel Mohen, Jean Bazaine and many others wrote about Junek's impact on French and Croatian painting.
[4] It has been argued that Leo Junek was the inspiration for Miroslav Krleža's character Filip Latinovicz, in The Return of Philip Latinowicz.
[10] Leo Junek's painting ranged from a loose Post-Impressionist, figurative style to a more Fauvist and Cubist approach in his later years.
[2] In a letter to Vera Nikolić Podrinska, he explains that pieces like Palestrina's Mass, Couperin's Prelude for harpsichord, or Debussy's Sonata for flute, viola and harp, best illustrated the "structure" of painting that he so dearly wanted to figure out.
[2] In a letter to Vera Nikolić Podrinska on 29 June 1951, Junek said: "Cézanne revealed to me that a stain can be extracted from a displayed object and analysed independently.