Police rushed to Tesco Express in Longridge Road following reports of an assault at around 8.55pm on Wednesday (October 7).
A man had reportedly entered the store and attempted to steal alcohol before arguing with a security guard.
He then allegedly pulled a knife from his back pocket before attacking the guard, resulting in the victim suffering "minor head and wrist injuries."
Officers have since confirmed a 25-year-old man from Preston has been arrested on suspicion of robbery and assault. He remains in custody for questioning.
A spokesman for Lancashire Police said: "It was reported a man had entered the shop and attempted to steal alcohol before assaulting a security guard using a knife.
"The guard suffered minor head and wrist injuries. Officers attended and detained a man at the scene.
"A 25-year-old man from Preston has been arrested on suspicion of robbery and assault and is in custody."