Egon Jelinek, son of the photographer Paul Jelinek (1878–1940), was active in the Austrian NSDAP ("Hitler movement", Brigittenau) from 1921. In 1928 he joined the Vienna Heimatschutz and in 1929 the Styrian Heimatschutz around Walter Pfrimer. He was a member of the NSDAP and SA from 1932 and a supporting member of the SS from 1934. In April 1938, Paul Jelinek, also an NSDAP member, gave his photo studio at Wallensteinstraße 20 in the 20th district to his son, who had completed training as a photographer at the Graphische Lehr- und Versuchsanstalt in Vienna and from 1936 was a member of the Österreichischer Photographen Verein, which was increasingly infiltrated by the NSDAP. He was already working as an informant for the NSDAP intelligence service before 1938. In April 1938 he was appointed temporary head of the ostmärkische Fotografeninnung (Ostmark Photographers' Guild). After the guild's incorporation into the Reichsinnungsverband, he was appointed regional guild master for photography in the Ostmark and then Gaufachschaftsverwalter of the Deutsche Arbeitsfront (departmental administrator of the German Labour Front) and temporary head and then regional head of the film department of the NSDAP Kreisleitung II regional propaganda office. He was also chairman of the Arisierungskommission der Wiener Photographeninnung (Aryanization Commission of the Photographers' Guild), temporary administrator of Wilhelm Pollak's studio on Kriemhildplatz in the 15th district, und assessor for the Aryanization of the business belonging to Nachim Chefez and Arpad Gyarmati. Together with Gustav Nohynek he looted the photographer Wilhelm Pollak and his father Hugo Pollak and denounced both to the Gestapo, which led to the death of Hugo Pollak in Gestapo detention. After he had been enlisted in March 1940 into the Intelligence Service of the German Wehrmacht, he wrote antisemitic articles for the Allgemeine Photographische Zeitung on photography in the territories occupied by the Wehrmacht.

After being a prisoner of war for a short time, Jelinek moved in May 1945 from Vienna to St. Johann in Tyrol and in February 1946 opened a photography gallery at Schwimmbadweg 520. His studio in Vienna, which had been destroyed in an air raid, and the premises Aryanized by him were put into public administration and liquidated in 1945. Criminal proceedings opened in June 1947 on suspicion of registration fraud and high treason pursuant to §§ 8 and 10 of the Prohibition Act ended in October 1948 with an acquittal, because his Gau file could not be found and he was described in the judgment as a "Heimatschützer" (homeland protector) on account of his membership in the Heimwehr organizations. In 1949 he was tried by the Vienna Volksgericht for wilful injury to Hugo and Wilhelm Pollak through denunciation (§ 7 War Criminals Act). In March 1950 the court sentenced him to eight months' imprisonment and forfeiture of his assets. In March 1957 his sentence was deemed to have been served in accordance with § 15 of the NS Amnesty Act after he had already been pardoned in 1955 and exempted from the restrictions for "sühnepflichtige Personen" (persons liable for atonement).

From the project Durch das NS-Regime aus Österreich vertriebene und ermordete Fotografinnen und Fotografen und der Verbleib ihrer fotografischen Sammlungen (Subsidized by the National Fund of the Republic of Austria. Conducted by Walter Mentzel).