The midfielder was involved in a fight with two men, and a picture of the incident, apparently showing a shirtless Barton being held back by police and a woman, appeared on Twitter.
But Barton played down the incident and revealed he would not press charges.
"Not planning on pressing charges as its not that serious. The police have also got better things to do with their time," he wrote on Twitter.
"Can I just say a public thanks to the police last night as they were and have been today brilliant."
Ian Taylor, a spokesman for QPR, added: "Joey Barton was involved in an incident in Liverpool city centre in the early hours of Monday morning.
"Barton was on his way home from a night out with his girlfriend when two men sang offensive chants and then proceeded to hit the R's midfielder.
"Police were immediately on the scene and arrested one man.
"Barton decided not to press charges and left the scene with his girlfriend soon after. The club will be making no further comment."
Liverpool-born Barton has a long history of controversy on and off the pitch and has become well-known for his voicing his opinions about football and the world at large on Twitter.
In 2004, Barton, then playing for Manchester City, hit the headlines after he stubbed out a cigar in the eye of apprentice Jamie Tandy.
His time at City also included an ugly incident when he left team-mate Ousmane Dabo looking like "the elephant man" after a training ground brawl.
Barton was given a six-month jail term in 2008 after admitting assault and affray during an incident in Liverpool.
Last month, he was given a 12-match ban by the Football Association (FA), after being sent off during QPR's defeat at Manchester City on the final day of the Premier League season.
His future at QPR remains in doubt as the club are also carrying out an internal investigation into the incident at City, which saw him elbow Carlos Tevez, kick out at Serio Aguero and then attempt to headbutt Vincent Kompany.
Source: AFP
Source: AFP