A baby boy died after he was found drenched in his mother’s blood — as she apparently tried to slash her own wrists with a boxcutter inside the bathroom of a Queens home Monday, cops and sources said.

The 15-month-old was found unconscious and unresponsive inside the bathroom of the private house on 157th Street near 108th Avenue in Jamaica around 1:30 p.m., according to police and sources.

A 28-year-old woman who sources identify as the tot’s mom was found with slash wounds to her wrists, authorities said.

Both mother and son were taken to Jamaica Hospital Medical Center, where the little boy was pronounced dead and his mom was listed in stable condition, cops said.

When hospital staff washed the toddler, it became clear that he was not stabbed or slashed — and that the blood was actually his mom’s, according to the sources.

The circumstances of the boy’s death remain under investigation.

The mother and son were alone in the bathroom when the incident happened, the sources said.

A nearby bodega worker told The Post that the toddler’s parents would occasionally come into the store to buy milk and water, and that he believed the couple had been living separately.

The worker recalled seeing a crying woman run out of the house and wave to him, and the bandaged mother being taken outside as authorities arrived at the home on Monday.

“The lady ran out of the house, and the man pulled up in the car and came to the house. I don’t know if he’s the father, but he came at the same time the police came,” the man, who wished not to be identified, described.

“I think she got cut because she had [bandages] on her arms when she come out of house,” he said. “She was taken out, her eyes were closed. Everybody was thinking she was dead.”

“It’s sad what happened. I feel terrible when I see the police running.”

The city medical examiner’s office will officially determine how the child died, and no arrests have been made, cops said.