Ernst Peschl came from a family of brewery owners. He was born to Eduard Ferdinand Peschl and his wife, Ulla (née Adler) in 1906.

After finishing secondary school in 1925 in Passau, Peschl started studying mathematics, physics, and astronomy in Munich. He received his doctorate in 1931 from the University of Munich under the supervision of Constantin Carathéodory with a dissertation titled *Über die Krümmung von Niveaukurven bei der konformen Abbildung einfachzusammenhängender Gebiete auf das Innere eines Kreises; eine Verallgemeinerung eines Satzes von E. Study* ("On the curvature of level curves of the conformal mapping of simply connected domains to the interior of a circle: A generalization of a theorem of Eduard Study"). This was followed by some years spent working as an assistant with Robert König in Jena and Heinrich Behnke in Münster. He habilitated in 1935 at the University of Jena. Peschl took up a visiting professorship at the University of Bonn in 1938, and was subsequently promoted to extraordinary professor there.

Under pressure Peschl became a member of the Nazi Party and the paramilitary *Sturmabteilung*, but he avoided any activity within either organization and ended SA service after a year. From 1941 to 1943 he was drafted as a French interpreter for the *Wehrmacht*. From 1943 to 1945 he worked at the German Aviation Research Institute in Brunswick, which exempted him from further military service during World War II.

After the war Peschl became the director of the Institute of Mathematics in Bonn, and in 1948 he became a full professor there. He promoted applied mathematics and established the Institute for Instrumental Mathematics in Bonn which evolved into the Society for Mathematics and Data Processing. He led the Society with Heinz Unger from 1969 to 1974.

Ernst Peschl's main areas of research were geometric complex analysis, partial differential equations, and the theory of functions of several complex variables.

Peschl was the doctoral advisor of Claus Müller, Friedhelm Erwe, Karl Wilhelm Bauer, Bernhard Korte, Stephan Ruscheweyh, and Karl-Joachim Wirths, among others.

Peschl received an honorary doctorate from the University of Toulouse in 1969 and another honorary doctorate from the University of Graz in 1982. For his fruitful collaboration with French mathematicians, the French government awarded him an *Officier des Palmes Académiques* in 1975.

Peschl was a regular member of the North Rhine-Westphalian Academy of Sciences, the Bavarian and Austrian Academies of Sciences and a corresponding member of the *Académie des Sciences, Inscriptions et Belles-Lettres* in Toulouse. He was awarded the Pierre Fermat Medal and the Medal of the University of Jyväskylä, Finland, in 1965.

Peschl married Maria Stein, a physician, in 1940, and had one daughter, Gisela.

*Über die Krümmung von Niveaukurven bei der konformen Abbildung einfachzusammenhängender Gebiete auf das Innere eines Kreises. Eine Verallgemeinerung eines Satzes von E. Study* ("On the curvature of level curves of the conformal mapping of simply connected domains to the interior of a circle: A generalization of a theorem of Eduard Study"), *Mathematische Annalen* 106, 1932, pp. 574–594
*Zur Theorie der schlichten Funktionen* ("On the theory of schlicht functions"), Crelle's Journal 176, 1937, pp. 61–94
*Über den Cartan-Carathéodoryschen Eindeutigkeitssatz* ("On the Cartan-Carathéodory uniqueness theorem"), Mathematische Annalen 119, 1943, pp. 131–139
*Analytische Geometrie* ("Analytic geometry"), *Bibliographisches Institut* ("Bibliographical Institute"), Mannheim 1961
*Funktionentheorie* ("Complex analysis"), *Bibliographisches Institut*, Mannheim 1967
*Differentialgeometrie* ("Differential geometry"), *Bibliographisches Institut*, Mannheim 1973, ISBN 3-411-00080-5