After completing his education, Pfeffer trained as a dentist and jaw surgeon, obtained a license to practice in 1911 and opened a surgery the following year in Berlin.

Pfeffer was granted custody of the boy and raised him alone until November 1938, when the rising tide of Nazi activity in Germany, as well as the Kristallnacht, persuaded him to send his son into the care of his brother, Ernst, in England.

Werner Pfeffer emigrated to California in 1945 after his uncle's death and changed his name to Peter Pepper, later establishing a successful office supplies company under that name.

In 1936, Fritz met a young woman, Charlotte Kaletta (1910–1985), born in Ilmenau, Thuringia, in central Germany, who shared his history of a broken marriage.

They were there for two years before the German invasion, and subsequent anti-Jewish laws prohibiting cohabitation of Jews and non-Jews forced them to officially separate and register under different addresses.

Anne's irritations and growing dislike of Pfeffer led to complaints and derisory descriptions of him in her diary, against which his son Werner and wife Charlotte defended him once the book was published.

With the rest of the group and two of their protectors, Johannes Kleiman and Victor Kugler, Pfeffer was taken to the Nazi headquarters at the Euterpestraat in Amsterdam-South, then to a prison for three days before being transported to the Westerbork transit camp on 8 August.

[citation needed] Werner Pfeffer remained in touch with Otto Frank and had the opportunity to meet Gies shortly before dying of cancer in 1995, to thank her for her attempt to save his father's life.

[5] In her memoir, Miep Gies writes that "The photos of Dr. Pfeffer reveal the handsome, cultured man I knew, rather than the buffoon that Anne so unkindly described in her diary.

"[6] Ed Wynn's portrayal of Pfeffer (as Dussel) in George Stevens' film The Diary of Anne Frank (1959) earned him a nomination for an Academy Award as Best Supporting Actor.