In the early 1960s, he created an abstract painting that was subsequently defamed as Western and decadent and excluded from all exhibitions. It was not until 1968, during the Prague Spring, that the exhibition "5 Young Artists" (Bertalan, Cotosman, Flondor, Molnar and Sayler) at the Galeria Kalinderu in Bucharest showed abstract-constructivist art in Romania for the first time. This was the breakthrough. Sayler moved to Bucharest and was able to exhibit abroad, but he was not allowed to travel there. In 1971, the political climate changed. The Reform Spring in Bucharest came to an end, and after that Sayler's works could not be exhibited in the Eastern Bloc. In addition, Sayler gave several interviews to the foreign press and as a result became even more isolated.

After emigrating to Germany in 1972, Sayler moved his center of work and life to Nuremberg, where he worked as a professor at the Academy of Fine Arts from 1992 to 2005, in addition to his artistic work.

In 1975 he exhibited his works for the first time at the Grand Palais in Paris. This was followed by solo exhibitions in renowned international galleries, the Galerie Grare in Paris, the Galerie Hermanns in Munich, and later in the Galleria Lorenzelli in Milan and the Galeria Edurne in Madrid. His works have since been shown in many Western European countries as well as in Brazil, Japan and the United States. In 1990, after the fall of the Iron Curtain, retrospectives of Diet Sayler's work were also shown in Eastern Europe, at the Czech Museum in Prague, the Vasarely Museum in Budapest, and the National Museum in Bucharest.

The exhibition series "konkret" in Nuremberg, which Sayler initiated and supervised from 1980 to 1990, attracted international attention. About 100 artists participated, including Dan Flavin, Ellsworth Kelly, Kenneth Martin, Vera Molnár, François Morellet, Aurélie Nemours, Mario Nigro, Leon Polk Smith, and Jesús Rafael Soto. In 1988 Sayler curated the Franco-German exhibition "Construction and Conception" in Berlin.

In the same year he received the Camille Graeser Prize in Zurich. In addition to exhibitions of paintings, prints, sculptures, and photographs, a number of site-specific installations have been shown at Galerie Grare, Paris; Palazzo Ducale, Genoa; East West Gallery, New York; St. Peter's, Cambridge; Gallery A, London; Ely Cathedral, Ely; University Gallery, Pilsen, Czech Republic; MUWA, Graz, Austria; Museo CAMEC, La Spezia, Italy.