Picerni joined the United States Army Air Forces during World War II and served as a B-24 Liberator bombardier in the China-Burma-India Theater. He flew twenty-five combat missions with the 493rd Bomb Squadron of the 7th Bomb Group and received the Distinguished Flying Cross.
Picerni married former ballet Dancer Marie Mason, in 1947. They settled in Tarzana, California to raise their family; they had eight children and ten grandchildren. Two of Picerni's children predeceased him.
As a young actor returning from the war, Picerni appeared in military pictures: in Twelve O'Clock High (1949) as a bombardier and as Private Edward P. Rojeck in Breakthrough. This led to a Warner Brothers contract and a succession of roles at that studio including a Portuguese Socialist "Red" agitator in 1952's The Miracle of Our Lady of Fatima, the hero of the 1953 horror classic, House of Wax. After his departure from Warners, he appeared with Audie Murphy in Universal Studio's To Hell and Back.
In 1954, Picerni was cast as the outlaw Rube Burrow in the syndicated western television series Stories of the Century, starring and narrated by Jim Davis. That same year, he had a role in the pilot episode for the 1957-58 NBC detective series, Meet McGraw.
Between 1957-60, Picerni was cast three times in different roles, the last as Duke Blaine, on the ABC/Warner Brothers western series, Colt .45, starring Wayde Preston.
Picerni made three guest appearances on Perry Mason during its nine-year run on CBS. In 1958 he played Charles Gallagher in "The Case of the One-Eyed Witness", and defendant Army Sgt. Joseph Dexter in "The Case of the Sardonic Sergeant". In 1963, he played murderer Walter Jefferies in "The Case of the Bouncing Boomerang". In 1964, he appeared in The Fugitive (TV series), in the episode "Search in a Windy City".
After Italian organizations began to complain about the use of Italian Gangsters on ABC's, The Untouchables, starring Robert Stack as G-man Eliot Ness, Picerni joined the cast in 1960 as Ness's number-one aide, Lee Hobson, a role that he played for the duration of the series. (He was also seen in the program's pilot, playing Tom Lugari.) He also portrayed Ed Miller on O'Hara, U.S. Treasury (1971-1972) and was featured as Dan Garrett on The Young Marrieds (1964-66)
In 1967, Paul appeared with his daughter Gina Picerni in the episode "The Chameleon" of the popular show My Three Sons.
His autobiography, Steps to Stardom: My Story, written with the help of Tom Weaver, was published by BearManor Media in 2007.
Picerni died from a heart attack on January 12, 2011 in Palmdale, California. Picerni is interred at the Roman Catholic San Fernando Mission Cemetery.
