Cops have arrested a teen for the death of a 9-month-old boy left in his care.

Martin Quirindongo, 17, of Brooklyn, has been charged with first-degree murder and second degree manslaughter for the death of Ryan Ferrer, who died from blunt-impact injuries Tuesday. The Medical Examiner’s Office ruled the death a homicide yesterday.

The baby suffered bleeding in his brain, and his internal organs were bruised and cut, a spokesperson for the ME told The Post. Authorities said Quirindongo — who was busted in 2009 for robbery — was baby-sitting the infant at the family’s Bronx apartment Tuesday morning while the mother was at work.

Police responded to a 911 call, and said the child was unconscious when they arrived at the Marble Hill apartment.

Ryan later died at a hospital.