The incident happened shortly after 9:30 a.m. Monday at the New Jersey Avenue beach.
According to police, the child was apparently drowning and his father entered the water to save him.
The child was able to make it to the shoreline, but the father began to struggle in the water.
Police say a retired police officer from New York retrieved a boogie board and attempted to rescue the father from the water.
The beach patrol chief and firefighters then arrived and assisted both men to shore.
The father was unresponsive and was given CPR by firefighters.
He was taken to the hospital where he died.
The 11-year-old was also taken to the hospital for treatment.
The Atlantic City Beach Patrol was off-duty at the time, police say, but members responded after hearing about the incident.