The midfielder popped into the Mathew Street bar with a group of friends and was pictured with musician Marc Kenny after his set.
Marc, who lives in New Brighton, often plays at the Cavern with his Beatles tribute band Paperback Writers but was performing solo when the Anfield star came into the pub.
Marc told ECHO: "It was a shock when I saw him, there are quite a few famous faces on the cavern walls of other celebrities that have been in but it certainly was a surprise seeing Philippe.
"I'm a massive Liverpool & Coutinho fan and I play at Anfield on match days either on outside stages or within the ground but it was great to see him enjoying the atmosphere here."
The 24-year-old Brazilian footballer has been playing for Liverpool since 2013 and has been a fan favourite since his debut.
Coutinho is often spotted in Liverpool with his teammates and his wife Aine but this is the first time he has been spotted at the city landmark.
Marc added: "He was with a few friends when he entered.
"He told me afterwards that he had enjoyed my set so that made meeting him even better."