The children, a three-year-old girl and a one-year-old boy, were injured in the fire on Friday.
The Wilmington Fire Department said on Monday that the girl was listed in serious condition at A.I. DuPont Children's Hospital and is showing 'much improvement.'
The boy is at Children's Hospital in Philadelphia and is listed as critical but is showing some improvement, firefighters said.
The fire broke out in the second floor of their grandmother's row home in the 1100 block of Pleasant Street around 12:20 p.m. Friday.
Firefighters were on the scene within minutes, and began efforts to rescue two children who were trapped inside.
Only the Action Cam was on the scene as Second Ladder Company Lieutenant Eric Haley and Senior Firefighter Neil Skinner first rescued the children.
The fire was discovered in a second floor rear bedroom and extinguished within 10 minutes. Fire damage was contained to the one house, but the homes on either side had smoke damage.
The cause of the fire remains under investigation by the fire marshal's office in Wilmington, and they haven't yet determined whether there were any working smoke detectors in the home.The toddlers had been in the care of their grandmother, while their mother was at work. The grandmother escaped the burning home without injury.