The rescuers contacted the South Wales Fire & Rescue Service, which dispatched a crew from the nearby Whitchurch Fire Station.
The firefighters reached the seagull and the RSPCA took the bird to a local veterinarian.
"This was a bit of a miraculous rescue for this gull. I feared the worst when I saw the poor thing impaled on a television aerial," RSPCA inspector Sophie Daniels said.
"Fortunately, firefighters were able to help us out and come to the gull's aid -- and remarkably, despite the painful ordeal, he seems to have few welfare concerns. We are always so grateful for their help in these situations as they have the specialist equipment to reach animals in a fix in high places," she said.
"After being checked over by vets, we transferred the gull to a wildlife specialist. Rehabilitation and care is expected for approximately ten days, and then this gull can be returned to where he belongs -- the wild," Daniels said.
