William Klinger, who lived in Gradisca d'Isonzo, a town in Friuli-Venezia Giulia, was shot in the head in Astoria Park, in New York’s Queens area, according to US media reports.
He was found face down by two women and later died in hospital.
The 42-year-old was a specialist in communist history and was in the city for a conference on the former Yugoslavia.
Police arrested Alexander Bonich, a Croatian who also lived in Italy, on Monday morning, The New York Post reported.
Bonich was hired by Klinger to find him lecturing work and was captured on CCTV at two different stores in Queens with his employer before the murder.
He reportedly told police he killed Klinger over a failed property deal between the two in Italy.
Bonich was charged with murder, criminal possession of a weapon and tampering with physical evidence after he was seen getting rid of Klinger’s belongings from his apartment, the newspaper said.