The man, whom police did not identify, accidentally toppled Dom Sebastiao’s statue after climbing up to its pedestal outside the ornate Rossio railway station in central Lisbon just before midnight on Tuesday.
He tried to flee the scene but police caught him. He will appear before a judge at a later date.
The child-sized statue of the sad-eyed, sword-wielding king stood in a niche between two horseshoe-shaped arches at the entrance to the station. Completed in 1890, the station is a protected monument.
Dom Sebastiao, who ruled between 1557 and 1578, is a tragic figure in Portuguese history, dying in battle at the age of 24 during a crusade of his own making in Morocco.
His body was never properly identified, giving rise to a legend that the king would one day return to claim his throne and save Portugal in times of trouble.