As two of the suspected thieves distracted staff at a museum in Offenburg, southwestern Germany, the other two clambered on a display case, removed a rhino head from a wall and smashed off the horns with hammers, police said.
"Then everything happened in the blink of an eye," police said in a statement.
"The two men stuffed the horns into a bag and left the museum. At the same time, the other two lost interest in their chat with staff members and followed their accomplices," the statement added.
The rhino head was left behind during the suspected robbery, which happened on Saturday afternoon, according to authorities.
Rhinoceros horn is especially prized in Asia where many consider it to have aphrodisiac and disease-fighting properties.
The perpetrators "acted with unbelievable audacity," the police said, adding: "The way they carried it out leads one to believe that this is an international, well-organised group."
Similar thefts have occurred throughout Europe, with some museums taking the unusual step of replacing their rhino horns with fake ones to deter robberies.
Rhino horns can fetch between €25,000 and €200,000 ($33,000 and $265,000) depending on their size.