"Hello human friends, I am Reem-C," said one of the guest exhibits, a 1.65-metre (five-and-a-half-foot) humanoid robot weighing 80 kilos (176 pounds).
Robots big and small showed off their skills at dancing, cooking and even training accident victims to walk again.
The 2014 International Conference on Humanoid Robots runs until Thursday at Carlos III University in the Spanish capital.
"There is quite a big explosion of robots currently," said one of the participants, Frederik Bengtsson, a Swedish student.
One of 430 participants from 31 countries, he entered a competition at the congress to programme some of the robots.
"The technology is getting cheaper and faster so it's a really fast-growing area, like computing a few years ago," he said.
Researchers are now trying to programme emotional responses in robots, said another expert, Santiago Martinez from Carlos III's Robotics Lab.
"But making a machine that can think is complicated," he said. "We will not see it in the near future."