Pearlroth attended university in Kraków, Poland, planning to become a lawyer, but events of World War I took him away from his studies. He came to America in 1920. Working in a New York bank in 1923, he learned from a friend that Robert Ripley was looking for a polyglot. Ripley needed someone capable of researching foreign newspapers to locate material for his syndicated Ripley's Believe It or Not! panel.
Since Pearlroth knew 11 languages, he was hired to do Ripley's research and soon began doing the picture research as well. He usually worked ten hours a day, six days a week in the New York Public Library's Main Reading Room. The library estimated that Pearlroth examined some 7,000 books every year, meaning that he researched in more than 350,000 books during decades of work on Believe It or Not!.
Married for more than half a century, Pearlroth and his wife lived in Brooklyn at Newkirk Avenue and East 16th Street. For 52 years, he took the subway into Manhattan in the morning and worked at his office until noon, answering some of the 3000 letters that arrived each week from readers all over the world. Instead of having lunch, he then went to the library where he worked through the afternoon and evening, taking half an hour for dinner. When the library closed at 10pm, he headed back to Brooklyn. He sometimes worked on Sundays if he fell behind in locating what he called "believe-it-or-nots." His deadline was on Friday, and he always worked several weeks in advance.
By the 1940s, Pearlroth and Ripley had some 80 million readers worldwide. During the first 26 years, Pearlroth simply gave Ripley whatever his research had turned up. After Ripley's death on May 27, 1949, King Features Syndicate took over Believe It or Not!, and Pearlroth continued for the next 26 years to work for syndicate editors, who required him to submit exactly 24 items each week. Pearlroth usually worked anonymously, but on Ripley's Believe It or Not! 50th Anniversary Edition (Pocket Books, 1968), he is credited as "Research Director."
For 25 years, Pearlroth also wrote a weekly column, "Your Name," about the origins of Jewish surnames, for the Jewish Post of New York. His son Arthur Pearlroth was the Economic Development Counsel for the South Bronx Development Office.
Although Norbert Pearlroth never missed a deadline, King Features replaced him in 1975. As a freelancer, he received no pension or royalties from the many collections and reprints that sold in the millions, but Ripley did give him a bequest of $5,000 and pay for Pearlroth's son's schooling.
He died in 1983 of heart and kidney diseases at Maimonides Hospital in Brooklyn.