He studied at the Kyiv Art School (1912–1914), and from 1917 - at the icon and fresco workshop of the Ukrainian Academy of Arts (later - the workshop of monumental painting) under the leadership of Mykhailo Boychuk. He graduated from the Ukrainian Academy of Arts in 1922. From 1922 he taught drawing at the Kyiv Art and Industrial College, and later worked at the Kyiv Art Institute, where he taught monumental painting, headed the department of theatrical and decorative art (1930–1934), and after World War II was a professor of the drawing department (1944–1950). At the same time, he taught at the Institute of Postgraduate Studies of the Academy of Architecture of the Ukrainian SSR.
In the 1920s, he actively worked in the field of propaganda art: he created posters, designed state institutions and revolutionary holidays, and was engaged in theatrical scenography. He worked with theaters in Kyiv and Odessa, designed the performances "Haydamaki" by Taras Shevchenko, "The Green Parrot" by Arthur Schnitzler, "The Blue Prince", and also made sketches of scenery and costumes for the performance "The Thresholds Are Beating". During World War II, he was evacuated to Samarkand, where he worked on political posters, graphic series, and participated in the creation of "TARS Windows".
He worked in the fields of easel painting, graphics, posters, and theatrical and decorative arts. Early works created under the influence of Boychukism are distinguished by the constructiveness of form, generalization of composition, and expressive plasticity ("Woman at the Table," "Worker's Head," "Strike Broken," "Printer Woman," "January Uprising in Kyiv"). In the 1930s, the artist gradually moved away from avant-garde searches, turning to the principles of socialist realism. His later portraits, landscapes, and graphic cycles ("Samarkand," "Zagorsk," "Kyiv-Kaniv," "On the Way to Taras Shevchenko's Grave") combine the academic school of drawing, analytical form, and lyrical interpretation of nature. Among the famous paintings are “Holiday”, “Streets”, “Self-portrait” (1917), “Arrest of a Pauper” (1934), “M. Shchors in Intelligence”, “Death of M. Shchors” (1937), “Fascist Curtain” (1943, co-authored).
Ieleva participated in art exhibitions since 1917, exhibited his works at exhibitions of the ARMU (1925–1932). The artist’s personal exhibitions were held in Kyiv in 1940, 1945, 1955 (posthumous) and 2008 (retrospective).
The works of Konstantin Ieleva are kept in the National Art Museum of Ukraine, the National Museum in Lviv, the Museum of Theater, Music and Cinematography of Ukraine, the funds of the National Academy of Fine Arts and Architecture and private collections.
Kostyantyn Ieleva is one of the leading representatives of the Mykhailo Boychuk school, who combined the traditions of monumental art with the graphic culture of drawing, theatrical scenography, and pedagogical activity. His work reflects the evolution of Ukrainian art from the avant-garde searches of the 1920s to the artistic practice of the mid-20th century, and his pedagogical legacy has significantly influenced several generations of Ukrainian artists.