Officers were called to the Emporium bar in Clitheroe at about 22:00 BST on Wednesday following reports a 23-year-old man had been assaulted.
Lancashire Police said the man had not needed hospital treatment.
A spokesman said officers were looking into “differing accounts” of what happened and no-one had been arrested.
The scuffle happened outside the Emporium, a spokesman for the bar said.
Moyes was sacked as United’s manager in May after 10 months in the role.
Before he took over at the club, he had been in charge at Everton for more than a decade.