Philip Bialowitz before the trial against John Demjanjuk in 2010. Mr. Demjanjuk was convicted of being a collaborating guard at Sobibor, a secret Nazi death camp. CHRISTOF STACHE, VIA ASSOCIATED PRESS

Philip Bialowitz, a Polish Jew who escaped Sobibor, a secret Nazi extermination camp, in the aftermath of a dramatic prisoner uprising and bore witness to the horrors of the Holocaust in a powerful memoir and in courtroom testimony, died on Aug. 6 in Delray Beach, Fla. He was 90.

The cause was congestive heart failure, his son Joseph said. Mr. Bialowitz had spent much of the past year and a half in a hospital after being hit by a car.

Mr. Bialowitz’s tale of survival involved good fortune and courage in equal measure. As a teenager in his hometown, Izbica, in eastern Poland, he was marched with other Jews to a cemetery, where Nazi soldiers opened fire on them. He escaped death by pretending to be hit and lying for hours among bloody bodies.

He was later taken, with his brother Symcha and other family members, to Sobibor, a camp about 55 miles away, where it is estimated that 250,000 people, mostly Jews, were murdered in 1942 and 1943 by the Nazis.

As Mr. Bialowitz and his family arrived with other Jews, they were asked if any had professions. Symcha said, truthfully, that he was a pharmacist, and, untruthfully, that his brother was his assistant. That saved their lives. Separated on the spot from their relatives, who were doomed, they were put to work as slave laborers, performing tasks that included collecting the clothing and valuables of their dead brethren.

Some months afterward, on Oct. 14, 1943, the Jewish workers carried out an escape plan, enticing guards to relax their vigilance by offering up a hoard of salvaged leather jackets and boots. Several SS officers were killed with knives and hatchets that the prisoners had secreted away, and about 300 fled through the gates of the camp. Nearly all were recaptured, but the Bialowitz brothers were among the 50 or so who were not. Symcha died at 102 in 2014 in Israel.

Shortly after the escape, the Nazis began to dismantle the Sobibor camp, one of three (along with Treblinka and Belzec) built for the explicit purpose of killing under the auspices of Operation Reinhard, the Nazi code name for the extermination of Jews. The history of the place was so well concealed that the underground remains of the gas chambers were not unearthed until 2014, news of which Mr. Bialowitz said “was the best moment of my life.”

“The Germans tried to do everything they could to hide their crime,” he told the German news website Spiegel Online. “But now archaeologists have discovered the gas chambers. Sobibor will become better known, and it will serve as an educational center for future generations. This is a victory — not only for us as survivors, but also for the whole mankind.”

Fiszel Bialowicz was born on Dec. 25, 1925, in Izbica, a largely Jewish town, and his family was observant, though not Orthodox. His father was a tanner who produced leather for shoes, a business that the Nazis commandeered after they invaded Poland in 1939. His mother, the former Bajla Klyd, was killed in a mass shooting directed by the Nazi SS.

and in 1939. His mother, the former Bajla Klyd, was killed in a mass shooting directed by the Nazi SS.

After the war, Mr. Bialowitz lived for a time in a displaced persons camp in Germany, where he initially planned to go to Israel and study dentistry, but in 1950 he went to the United States.

He settled first in Columbus, Ohio, and later moved to New York City, where he lived in the Bronx and then Queens and worked as a jeweler in the diamond district in Midtown Manhattan. He married and divorced twice.

In addition to his son Joseph, he is survived by a daughter, Simone Shlomi; two other sons, Jeffrey and Michael; 14 grandchildren; and 11 great-grandchildren.

Mr. Bialowitz, one of the final survivors of Sobibor (and believed to be the last Polish Jew among them), testified in 2010 at the trial in Germany of John Demjanjuk, who was later convicted of being a collaborating guard at Sobibor but was appealing the guilty verdict at the time of his death in 2012.

Mr. Demjanjuk had also been tried in Israel, where he had been accused of being a sadistic guard known as Ivan the Terrible at Treblinka. In 1988, he was found guilty of crimes against humanity and sentenced to death, but new evidence subsequently emerged that another man was most likely Ivan the Terrible, and the Israeli Supreme Court overturned the conviction in 1993.

Mr. Bialowitz devoted much of his later life to speaking and writing about his experiences, determined to keep alive the message that such evil is not only imaginable, but possible in the world, though he was philosophically disposed to emphasizing a human counterspirit.

“When my father would lecture, he would always talk about life before the Holocaust, how people resisted, and how they lived after the Holocaust,” Joseph Bialowitz, who worked with his father on a 2008 memoir, said in an interview on Friday.