An ambulance was called to the Apple Blossom Learning Tree Day Care Center at 1601 Lombard Street at 4:32 p.m.
The baby was found unresponsive in a crib at the daycare.
Medics rush the child to Children's Hospital of Philadelphia where she was pronounced dead a short time later.
The department's special victims unit is investigating.
At this time, it has not been determined if foul play is suspected.