A few references to men changing into wolves are found in Ancient Greek literature and mythology. Herodotus, in his Histories, wrote that the Neuri, a tribe he places to the north-east of Scythia, were all transformed into wolves once every year for several days, and then changed back to their human shape. This tale was also mentioned by Pomponius Mela.

In the second century BC, the Greek geographer Pausanias related the story of King Lycaon of Arcadia, who was transformed into a wolf because he had sacrificed a child in the altar of Zeus Lycaeus. In the version of the legend told by Ovid in his Metamorphoses, when Zeus visits Lycaon disguised as a common man, Lycaon wants to test if he is really a god. To that end, he kills a Molossian hostage and serve his entrails to Zeus. Disgusted, the god turns Lycaon into a wolf. However, in other accounts of the legend, like that of Apollodorus' Bibliotheca, Zeus blasts him and his sons with thunderbolts as punishment.

Pausanias also relates the story of an Arcadian man called Damarchus of Parrhasia, who was turned into a wolf after tasting the entrails of a human child sacrificed to Zeus Lycaeus. He was restored to human form 10 years later and went on to become an Olympic champion. This tale is also recounted by Pliny the Elder, who calls the man Demaenetus quoting Agriopas. According to Pausanias, this was not a one-off event, but that men have been transformed into wolves during the sacrifices to Zeus Lycaeus since the time of Lycaon. If they abastain of tasting human flesh while being wolves, they would be restored to human form nine years later, but if they do they will remains wolves forever.

Pliny the Elder likewise recounts another tale of lycanthropy. Quoting Euanthes, he mentions that in Arcadia, once a year a man was chosen by lot from the Anthus' clan. The chosen man was escorted to a marsh in the area, where he hung his clothes into an oak tree, swam across the marsh and transformed into a wolf, joining a pack for nine years. If during these nine years he refrained from tasting human flesh, he returned to the same marsh, swam back and recovered his previous human form, with nine years added to his appearance. Ovid also relates stories of men who roamed the woods of Arcadia in the form of wolves.

Virgil, in his poetic work Eclogues, wrote of a man called Moeris, who used herbs and poisons picked in his native Pontus to turn himself into a wolf. In prose, the Satyricon, written circa AD 60 by Gaius Petronius Arbiter, one of the characters, Niceros, tells a story at a banquet about a friend who turned into a wolf (chs. 61-62). He describes the incident as follows, "When I look for my buddy I see he'd stripped and piled his clothes by the roadside... He pees in a circle round his clothes and then, just like that, turns into a wolf!... after he turned into a wolf he started howling and then ran off into the woods."

Early christian authors also mentioned werewolves. In The City of God, Augustine of Hippo gives an account similar to that found in Pliny the Elder. Augustine explains that "It is very generally believed that by certain witches spells men may be turned into wolves..." Physical metamorphosis was also mentioned in the Capitulatum Episcopi, attributed to the Council of Ancyra in the 4th century, which became the Church's doctrinal text in relation to magic, witches, and transformations such as those of werewolves. The Capitulatum Episcopi states that "Whoever believes that anything can be...transformed into another species or likeness, except by God Himself...is beyond doubt an infidel.'

In these works of Roman writers, werewolves often receive the name versipellis ("turnskin"). Augustine instead uses the phrase "in lupum fuisse mutatum" (changed into the form of a wolf) to describe the physical metamorphosis of werewolves, which is similar to phrases used in the medieval period.