The man was arguing with the victim, identified as 44-year-old Ilona Ganzha, in their bedroom at 42A Country Drive North just before 3:40 p.m., when he stabbed her several times in the chest, police said.
The man then stabbed himself twice in the chest and slit his wrists, the NYPD said.
Ganzha was pronounced dead at the scene, while the suspect was rushed to Staten Island University Hospital in critical condition, police said.
Neighbors, who said the couple had four children, were shocked to learn of the alleged attack in the small, community-oriented development.
"They're a quiet family," said one man who declined to give his name. "You hear arguing, but it was nothing crazy."
Theresa Cirillo, who lives nearby, described the victim as a "very lovely woman" and said the family mostly kept to themselves.
"Nothing like this should happen to anybody," Cirillo said. "I feel so terrible that this happened."