Wiesenthal was widely believed to have been operating independently when Nazi Adolf Eichmann was captured in Austria in 1960, The New York Times said Thursday.
In the biography "Simon Wiesenthal: The Life and Legends," author Tom Segev said his review of a vast collection of Wiesenthal's private documents found he frequently worked for Israel as a Nazi-hunter.
"This requires us to adjust in some small way our view of history," Segev said in an interview with the newspaper.
Wiesenthal's role in Eichmann's capture has been disputed. Isser Harel, who headed the Mossad, said Wiesenthal deserved no credit, the book says. (Harel died in 2003.)
The biography says Wiesenthal, financed by the Israeli Embassy in Vienna, told the Mossad in 1953 that Eichmann was then hiding in Argentina, which ultimately resulted in his capture.
The book says Wiesenthal helped former Austrian President Kurt Waldheim fight claims he lied about his service in the German Army. Waldheim was also secretary-general of the United Nations, and accusations against him were never proven.
Weisenthal died at the age of 96. The Simon Wiesenthal Center in Los Angeles was named in his honor.