He is known for his work Rhōmaikē Archaiologia (Roman Antiquities), which describes the history of Rome from its beginnings until the outbreak of the First Punic War in 264 BC.

[2] Dionysius' opinion of the necessity of a promotion of paideia within education, from true knowledge of classical sources, endured for centuries in a form integral to the identity of the Greek elite.

[3] At some time after the end of the civil wars he moved to Rome, and spent twenty-two years studying Latin and literature and preparing materials for his history.

[5] His major work, entitled Roman Antiquities (Ancient Greek: Ῥωμαϊκὴ Ἀρχαιολογία, Rhōmaikē Archaiologia), frequently abbreviated Ant.

(Latin: Antiquitates Romanae), narrates the history of Rome from the mythical period to the beginning of the First Punic War in twenty books, of which the first nine remain extant while the remaining books only exist as fragments,[2] in the excerpts of the Roman emperor Constantine Porphyrogenitus and an epitome discovered by Angelo Mai in a Milan manuscript.

[citation needed] In the preamble to Book I, Dionysius states that the Greek people lack basic information on Roman history, a deficiency he hopes to fix with the present work.

But he carefully consulted the best authorities, and his work and that of Livy are the only connected and detailed extant accounts of early Roman history.

[4] Dionysian imitatio is the literary method of imitation as formulated by Dionysius, who conceived it as the rhetorical practice of emulating, adapting, reworking, and enriching a source text by an earlier author.

[9] Dionysius carried out extensive research for his Roman history, selecting among authorities, and preserving (for example) details of the Servian Census.

[8]: 239 His first two books present a unified account of the supposed Greek origin for Rome, merging a variety of sources into a firm narrative: his success, however, was at the expense of concealing the primitive Roman actuality (as revealed by archaeology).

[8]: 241  Along with Livy,[12] Dionysius is thus one of the primary sources for the accounts of the Roman foundation myth, and that of Romulus and Remus, and was relied on in the later publications of Plutarch, for example.

Citing Fabius, Cincius, Porcius Cato, and Piso, Dionysius recounts the most common tale, whereby the twins are to be tossed into the Tiber; are left at the site of the ficus Ruminalis; and rescued by a she-wolf who nurses them in front of her lair (the Lupercal) before being adopted by Faustulus.

According to Plutarch, lupa (Latin for "wolf") was a common term for members of her profession and this gave rise to the she-wolf legend.

[16] Before the actual construction of the city began, Romulus made sacrifices and received good omens, and he then ordered the populace to ritually atone for their guilt.

A system of patronage (clientela), a senate (attributed by Dionysius to Greek influence) and a personal bodyguard of 300 of the strongest and fittest among the nobles were also established: the latter, the celeres, were so-named either for their quickness, or, according to Valerius Antias, for their commander.

[24] Another source claims that Romulus was killed by his Roman countrymen after releasing hostages, showing favoritism, and excessive cruelty in his punishments.