We have only scanty pieces of information about the life of Cassius Felix. Several clues lead us to believe that he was a Roman citizen living in Africa between the fourth and the fifth century AD. Manuscript Parisinus lat. 6114, carrying the text of his treatise De medicina, calls him 'Cirtensis' and dates the work to 447 AD, at the time of the consulship of Ardabur and Calepius (Sabbah). A funerary inscription discovered at  Cirta (CIL VIII 7566) records the death of a Cassius Felix. If the person mentioned in the inscription is indeed an ancestor of the author of the De medicina, the inscription would locate his family of origin in space, confirming the data reported by the Parisinus manuscript. Several elements in the text, both in language and content, strengthen the case for placing the author in an African context: even if Cassius Felix states in his preface his intention to write his work in Latin, he often uses words of Semitic origin, without feeling the need to justify his use of them (Adams), since he thinks they are in common usage (see e.g. 31.1, 32.4, 72.5). He offers detailed comments on the stigmata on the faces of African women (31.1), which suggests direct observation. As for the date, a terminus post quem adds plausibility to the information reported by manuscript Parisinus lat. 6114 in its incipit: Cassius Felix refers three times (32.4, 42.21 and 69) to Vindicianus, physician and proconsul of the Province of Africa between 379 and 382 (Fraisse). An anonymous African hagiographic work,De miraculis sancti Stephani protomarthyris, probably written in the first half of the fifth century AD  (PL XLI, 833-854) mentions a character called 'Felix', chief physician at Carthage; he seems to correspond to Cassius Felix the author of the De medicina. The episode is set in a time that is compatible with the supposed date of the composition of the De medicina. Moreover, the chief physician at Carthage and the author of the De medicina use similar phrases (omnipotenti Domino in PL XLI, 854; omnipotentis dei nutu in the praefatio) to disclose their religious beliefs (Sabbah). Cassius Felix was a learned person, a man of letter well versed in Greek and Latin, and very probably himself a physician. He describes in technical detail some of the operations, which suggests that he was not alien to the medical profession. He seems to suggest as much in his preface, when he says that he has decided to commit his breuiloquium to writing after ‘having practiced’ medicine for a long time.

If one gives credit to the hypotheses mentioned so far, one could offer the following summary: Cassius Felix was a physician from Northern Africa, a Christian, a descendant from a family which originated from Cirta. He was a learned man, definitely bilingual; he was born around the mid-fourth century AD; he practices medicine and taught it in his capacity of chief physician at Carthage. In 447, at an advanced age (see the Praefatio), he wrote the work now known under the title De medicina, with the goal of offering to his students a clear and exhaustive medical treatise, with special emphasis on practical usefulness.