He studied engineering and taught in the Jewish community's vocational school in Warsaw. From 1927 to 1934 he served as a member of the Warsaw Municipal Council, and in 1931 he was elected to the Polish Senate. On October 4, 1939, a few days after the city's surrender to the Nazis, Czerniakow was made head of the 24 member Judenrat, (Jewish Council) responsible for implementing German orders in the Jewish community.
German forces began preparing for mass deportations from the Warsaw Ghetto to the Treblinka death camp in July 1942 and the Jewish Council was ordered to provide lists of Jews and maps of residences. On July 22, 1942, the Judenrat received instructions that all Warsaw Jews were to be deported to East--exceptions were made for Jews working in German factories, Jewish hospital staff, members of the Judenrat and their families, and members of the Jewish police force and their families. Over the course of the day, Czerniakow was able to obtain exemptions for a handful of individuals, including sanitation workers, husbands of women working factories, and some vocational students. He was not, however, despite all his pleading, able to obtain an exemption for orphans. The orders further stated that the deportations would begin immediately at the rate of 6,000 people per day, to be supplied by the Judenrat and rounded up by the Jewish police. Failure to comply would result in immediate execution of some one hundred hostages, including employees of the Judenrat and Czerniakow's own wife. Realizing that deportation meant death, Czerniakow went to plead for the orphans. When he failed, he returned to his office and took one of the cyanide capsules he had been keeping for just such an occasion. He left a suicide note to his wife and one to his fellow members of the Judenrat, explaining: "I can no longer bear all this. My act will prove to everyone what is the right thing to do."
Czerniakow kept a diary from September 6, 1939, until the day of his death. It has been published in 1979 in the English language as the Warsaw Diary of Adam Czerniakow: Prelude to Doom.
Adam Czerniakow is interred in the Okapawa cemetery in Warsaw.