In 1580, when Antonio was four years old, after the birth of his brother Vincenzio, both his father and grandfather were together granted full Florentine citizenship by Grand Duke Francesco I de' Medici. In Tuscany, citizen status was an honor conferred to a small fraction of the population and often through inheritance at around the age of thirty. The fact that Neri Neri gained citizenship at the age of forty and did so together with his father, Jacopo, shows it was not legacy, but perhaps their medical prowess that lead to the award. This period also corresponds to the first appearance of the unique coat of arms that distinguish this branch of the family. The same arms adorn the central panel of the vestibule ceiling at the Neri's residence. Citizen status bestowed the advantage of direct representation in the government and the right to hold public office. It also carried responsibilities to the city, to its leaders and to the Church. One requirement of citizenship was possession of a domicile within Florence. The baptism register listed Antonio and all of his siblings as residents of San Pier Maggiore parish long before the citizenship grant. However, it is in the 1580s that we see the first reference to Neri Neri's ownership of the palazzo at what is now 27 Borgo Pinti.
Within a few years, Antonio's father would publish his work on cures for paralysis and by the end of the decade he was appointed personal physician to the new grand duke, Ferdinando de' Medici. The 1590's saw Antonio taking vows, and beginning his career in the Church. The road to priesthood ran on a parallel track to an apprenticeship in a trade. The completion of a trial period lead to becoming a novice at the age of sixteen, then deacon and finally priest. Meanwhile, Antonio's father, along with another doctor and two apothecaries was chosen by the entire Florentine College of Physicians to revise and update the famed Ricettario Fiorentino. This book was the gold standard of doctors and pharmacists throughout Europe. The Ricettario was the official reference for medicinal cures in Tuscany. The law required every apothecary to own a copy and to supply its listed formulas to customers. Many regard this volume as the first European pharmacopoeia. It was a systematic standardization of drug recipes and dosages. Throughout the Medici reign, updated editions appeared as knowledge progressed. The book is a major landmark in the history of medicine. The edition authored by Neri's father and colleagues, in 1597, proved so popular that in 1621 it was reissued without change.
There can be no doubt that Antonio's father and his work had a profound influence on the priest. In his book on glassmaking, L'Arte Vetraria, he proclaims his desire to publish his own work on chemical and medical [spagyric] arts, saying "I believe there is no greater thing in nature in the service of humanity." In his recipes he uses the terminology of physicians; adding chemicals in 'doses' and measuring 'ana' (in equal parts). In a 1608 letter to a friend, Antonio describes his great success with medicinal cures of Paracelsus, "to the great wonderment of Antwerp." The priest also references experiments he carried out in Brussels and at the Hospital of Malines.