After the end of the war, Fedorenko abandoned his wife and two children, who remained in the Soviet Union, and spent four years living as a war refugee in West Germany, working for the British from 1945-1949. Fedorenko emigrated to the United States from Hamburg in 1949 and was granted permanent residency status under the Displaced Persons Act. He initially resided in Philadelphia but later settled in Waterbury, Connecticut where he found employment as a brass factory worker. Fedorenko would reside in Waterbury for the next two decades.

While Fedorenko's life in the United States was quiet, he had been identified as a possible war criminal. Treblinka survivors identified him as a guard at the camp from a collection of photographs and documents that had been captured from the SS. In the mid-sixties his name and Waterbury, Connecticut address were included on a list of fifty-nine war criminals living in America. The list was compiled in Europe and Israel and forwarded to the Immigration and Naturalization Service (INS) in the United States.

He was granted U.S. citizenship in 1970, however and later retired to Miami Beach, Florida in 1973. In the mid-70s, Congressional Representatives Joshua Eilberg and Elizabeth Holtzman initiated a set of hearings that led the US Government Accountability Office (GAO) to investigate the handling of possible Nazi war criminal data. No mishandling was found, but as a result, a Special Litigation Unit for the investigation of Nazi war criminals was established in the INS. The information supplied in the sixties was now put to use. In 1977, the INS supplied information on Fedorenko to Justice Department prosecutors.

In 2005, a Russian documentary Secrets of the Century - Punishers: May 9th reported that in 1974 Fedorenko visited Crimea as a tourist, where he was recognized and this raised the interest of the KGB. Afterwards, the Soviet government contacted the White House and requested that the case of Fedorenko be reviewed.