The ear has the flexibility of a real ear, researchers at Massachusetts General Hospital in Boston told BBC.
Tissue engineering is a growing field in medical science, where substitute organs are made in the laboratory in the hope of using them to replace damaged ones.
"The US research team is working on artificial ears to help people born with malformed ears or who have lost them in accidents or trauma," said the study published in the Journal of the Royal Society Interface.
Earlier, the researchers had grown an artificial ear, the size of a baby's, on a mouse.
In the latest case, they took living tissues from cows and sheep and grew them on a flexible wire frame that has the 3D shape of a real human ear.
This was then implanted into a rat whose immune system they had suppressed enabling the ear to grow.
"We've demonstrated the first full-sized adult human ear on the rat model," Thomas Cervantes, who led the study, told BBC.
The case was significant for several reasons, he said.
"One - we were able to keep the shape of the ear, after 12 weeks of growth in the rat. And then secondly we were also able to keep the natural flexibility of the cartilage."
The cells were grown on a titanium wire scaffold that is modelled on the dimensions of a real human ear, taken from CT scans.
The new work showed that in theory it is possible to grow up enough cells - at least in animals - to make a full-size human ear.
"In a clinical model, what we would do is harvest a small sample of cartilage, that the patient has, and then expand that so we could go ahead and do the same process," said Cervantes.
He said he expected that the process could move into human clinical trials in about five years.