From the 8th century BC onwards, Greek colonies were established in the region, including the city of Cumae, located on the other side of the Gulf of Naples. Around the 7th century BC, the Etruscans settled in the area and competed with the Greeks for control of the region for more than 150 years. However, the true influence of these groups on the origins and subsequent development of Pompeii remains uncertain, as the archaeological evidence does not provide definitive conclusions.

Towards the end of the 5th century BC, the Samnites, another Italic people speaking the Oscan language, invaded and conquered the entire Campania region. At this historical moment, there is a marked decrease in the number of archaeological finds in the city, which has led some archaeologists to speculate that Pompeii may have been temporarily abandoned. If this abandonment occurred, it was short-lived, as until the mid-4th century BC, the city was part of the Samnite confederation and served as a port for communities located upstream.

The new Samnite rulers introduced their architectural style and expanded the city. It is believed that during this period, the Romans briefly took control of the city, although these theories have never been confirmed. In any case, it is known that during Samnite rule, the city was under the authority of a magistrate known as "Medix Tuticus," possibly with administrative and judicial functions, and that this title originated in the Oscan language.