He was 86 and lived in Silver Spring.
He was a graduate of Patterson Park High School, and from 1944 to 1946 served as an Army Air Corps tail gunner.
Mr. Fialkewicz remained in the Army Reserve, where he attained the rank of major.
He earned a bachelor's degree in 1948 from the University of Baltimore, and two years later, began working as an agent for the Federal Bureau of Narcotics. He worked in Detroit, Cleveland, Buffalo, Greensboro, N.C., Roanoke, Va., and Washington.
In 1967, he was given a special assignment to the U.S. Senate Subcommittee on Investigations. He transferred to Interpol in 1978, where he was a DEA agent supervisor.
He retired in 1981, but continued working as a fraud consultant to the National Association of Credit Managers.
In 1984, he went on staff as a senior investigator, working on major cases that were turned over to the Secret Service and FBI to complete, which in turn were handed to federal prosecutors.
He retired a second time in 1990.
Mr. Fialkewicz enjoyed spending time at his Ocean City beach house, boating, working in his yard and gardening. He was also an Orioles and thoroughbred racing fan.
Mr. Fialkewicz's wife of 59 years, the former Carmeline "Cam" Hammel, died in 2009.
He was a communicant of the Roman Catholic Church of the Resurrection, 3315 Greencastle Road, Burtonsville, where a Mass of Christian burial will be offered at 11 a.m. Wednesday.
Surviving are a stepson, Robert Hammel of Monterey, Calif.; a stepdaughter, Janice Pandit of Olney; two sisters, Emilia Chojnowski and Dorothy Smith, both of Baltimore; four grandchildren; 14 great-grandchildren; and two great-great-grandchildren.