Cincinnatus lived (if he truly did) in the early Republic, which is a murky period of Roman history. Guy Bradley describes it as "quasi-historical with mythological elements". That is, compared to the very earliest "Romulus and Remus"-type mythological early "history" of Rome, for the texts covering Early Republic, we can with fair certainty say that we do find some truly historical elements about the period. But, the record still has substantial mythological and idealising, biographical features that have to be taken with a grain of salt. The academic community can be bitterly divided over the historicity of any one detail about this period in Roman history.

The only written sources that survive extant from the Early Republic are very short and random inscriptions on physical artefacts, like dedications, numerical scratchings on pot sherds etc., but there are a couple of notable exceptions. The earlier, regal period Lapis Niger-text from the Forum, that appears to have been some sort of law, shows in the least that there was also a more complex written culture in some scale by the time of Cincinnatus. Whether this written culture included an interest in recording contemporary events and narratives in some form is debated, and even if it did, there is the question could any of it have survived to the 3rd. century BC when the Roman historiographical writing finally kicks off, both in the form of dry, list-like annalistic tradition, and then the Greek-type, narrative historiography 'proper' (Fabius Pictor, fl. c. 215–200 BC, generally considered the first Roman historian). These early historians may have had some real written documents from the early Republic to work with, like inscriptions, or private and official records - but it is highly unlikely they could have read or understood Old Latin. E.g. the Lapis Niger text still continues to evade modern scholars' attempts to crack it fully.

Among the 'archaic' transmitted texts that might have some genuine old orgins are the Fasti, chronological lists of important events and officials - notably the Fasti Capitolini is a document listing all the chief magistrates from the beginning of the city to the Augustan period. It is clear that this document at some point during the Republic becomes truly reliable and is based on surviving official records, possibly the Annales Maximi, annals supposedly kept by the pontifex maximus (the highest chief priest in Rome) from the very early Republican period (but how early? who knows). There are reasons to believe that the very earliest names on the Fasti are fictitious later inventions - the historicity of Rome's seven kings is much debated, and the earliest consuls have suspiciously fittingly patriotic names, referring to the Seven Hills of Rome and the city's mythological origins etc. Notably, Cincinnatus is listed on the Fasti, as the suffect consul of 460 BC, and then as dictator in 458 BC. The year of Cincinnatus' supposed second dictatorship in 438 BC is missing, because the parts covering 449–423 BC of the Fasti are lost. The Fasti is one of the reasons that most scholars will treat Cincinnatus as "most likely a truly historical" figure, but note that this is the part of the Fasti where we are somewhat at the threshold of "certain historicity".

If the annalists and Fabius Pictor did have some actual ancient Roman written records to work with, when the narrative of Cincinnatus as history started to be written down, they most likely were nothing much more spectacularly detailed than the Fasti. They also used some Greek historical writings about Roman history, at least those by Timaeus of Sicily, Diocles of Peparethus and Antiochus of Syracuse. None of this survives to this day, and we don't know very much about how reliable or detailed they were, and what the methodology and sources of these outsider historians were like.

Overall, oral history must have been among the most important sources for early Roman historians - historical events narrated through stories, songs, theatre plays and so forth. We don't know exactly what the early Roman historians possibly wrote about Cincinnatus, as their works have been lost, and it isn't until the Augustan period when we finally have a surviving, detailed account of Cincinnatus' heroics in the famous account given by Livy (who used the annalists and Pictor as his sources, among others). So, what we today know of Cincinnatus is a result of some 400 years of retelling his story mainly orally, and possibly perhaps some hazy trace of actually reliable written documents or/and accounts. And, Roman historiography wasn't as "neutral" or "objective" as historical writing today is; Livy's history has plenty of moralising and patriotic dazzle and bias that serve his contemporary audience.

All this, however, isn't a reason to dismiss the historical tradition completely. Plenty of the stuff concerning early Rome has been confirmed true via archaeological evidence etc.. But all this does mean that the parts covering early Republic in the tradition do have the characteristics of oral history. Cincinnatus' story is a prime example of this. His story was treated as actual history, but it serves above all as a moral exemplum about ideal Roman-ness (in the Livian period). Cincinnatus was a dazzlingly talented military man and political leader, but he had zero interest in selfish prestige, power or wealth. He used his talents only for the greater good at the time of crisis, recultantly "called from his plough", and then went straight back to his modest rural life in poverty. The exemplarity of Cincinnatus' character is why the story was important and orally retold for 400 years - not because of deep communal interest in any particular historicity of the details. There are, therefore, elements in the Cincinnatus' story in Livy that are rather suspect and are probably embellishment/exaggeration/Chinese Whispers-type broken transmission. It is, for example, often pointed out that Cincinnatus' "spectacularly crushing victory" over the invading Aequi in 458 BC couldn't have been anything of the like, since Livy very soon goes on to recount in a contradicting manner that the Aequi returned to attack Rome in 457 BC, and again in 455 BC.

To sum up; most scholars today would say that there is some 'true historical core' in the story of Cincinnatus, but also plenty of ideological hash and distortion. Exactly how much is just 'distortion' and what is 'true' would, however, be impossible to objectively delineate, because we simply have zero contemporary, or even anywhere near-contemporary, sources to Cincinnatus' acts and deeds, just the 400-year-old filtered 'hash'.