Handout footage showed five protesters in front of "Las Meninas," a famous painting by Diego Velazquez, holding banner with their demands.
The statement demanded intervention from Prime Minister Pedro Sanchez to help victims of one of the world's biggest food poisoning scandals.
Thousands of Spaniards suffered lung diseases that were later related to the consumption of processed rapeseed cooking oil. Thousands of others suffered debilitating syndromes for life.
A spokesperson for the El Prado museum and art gallery did not return phone calls seeking comment.