The slave, secretary, adviser, and later freedman of Marcus Tullius Cicero, from whom he took his first two names when he was manumitted, probably in 53 BC, on his 50th birthday. He remained in Cicero's employment until his former master's death, transcribing and editing his speeches and other works. After Cicero's death, Tiro may have posthumously published some of his poetry and jokes. Aulus Gellius, in his Noctes Atticae, tells us that he was a very educated man, who wrote several books on Latin usage and grammar, as well as smaller treatises on miscellaneous subjects and a pandectes, or encyclopaedia. It is said that he died in 4 BC, at the ripe old age of 100.

He is perhaps best known for the invention of Tironian Shorthand, or notae Tironianae, a secretary's shorthand used in the transcription of Cicero's speeches. It apparently consisted mostly of abbreviations for prepositions and case endings. Since no real scribal schools existed at the time, he is credited with training other scribes in the practice. The notation was widely used in the documents of the later empire, and, in a modified form, by the early church administration.