The worker, Ashford Geddes, 68, was stabbed multiple times on Wednesday around 9 a.m. on Lenox Avenue near 138th Street Street in Harlem, the police said.
A spokeswoman for the Salvation Army confirmed that Mr. Geddes was working for the organization.
The stepson, Waldean Elliot, 32, was charged on Wednesday night with murder and criminal possession of a weapon. The police said they did not know the nature of the dispute between the men.
Mr. Geddes, who lived several blocks from where he was stabbed, was taken to Harlem Hospital Center, where he was pronounced dead.
A Salvation Army official, Maj. James W. Betts, told NBC 4 New York in a statement that Mr. Geddes was a “valued employee.”
“Our thoughts and prayers are with his family and his partners in service here at the Corps,” the statement said. “We look forward to cooperating with the authorities as they search for answers related to this senseless act of violence.”