The incident at a pub in East Lothian was captured on security cameras.
Lothian and Borders Police said they had issued an arrest warrant for a man in connection with Sunday night’s attack in Tranent.
Publican Elliot Morgan said: “The CCTV we have at the pub is of an extremely good quality and you can see the guy pick up the bit of ear and put it in his mouth.
“He definitely didn’t spit it out. He swallowed it.
“It’s absolutely horrendous that my hard-working staff have to witness things like this when all they are trying to do is their job.”
A spokesman for Lothian and Borders Police said: “We have sent a report to the procurator fiscal and someone is now subject to an arrest warrant.”