He was the son of Claudio Achillini, an old family of Bologna.
He was of a very simplistic nature. He was unskilled in the arts of adulation and double-dealing to such a degree that his most witty and imprudent students often regarded him as an object of ridicule, even though they honored him as a teacher. He also possessed quite a lively disposition. According to a colleague's description, he was handsome, tall but well proportioned, cheerful, happy, often smiling, and affable. Achillini never married. His reputation among his colleagues was admirable and he was highly respected. And although Achillini was well-read and formidable in debate, he was said to be somewhat rigid and stiff in his lecturing. After his death, many people were extremely devastated.
He died in Bologna on August 2, 1512. He was buried on August 3, 1512 in St. Martin's Church. Among his notable discoveries, he is known as the first anatomist to describe the two tympanal bones of the ear, termed malleus and incus. In 1503 he showed that the tarsus (middle part of the foot) consists of seven bones, he rediscovered the fornix and the infundibulum of the brain. He also described the ducts of the submaxillary salivary glands.
In 1506, he was obliged to leave Bologna owing to the expulsion of the powerful Bentivoglio family of whom he was a partisan. He then went to Padua where he was appointed teacher of philosophy.
Alessandro Achillini began teaching when he was 21 years old. From the years 1484-1512, except 1506-1508, he was a professor of Medicine and/or Philosophy in the University of Bologna. During the 2-year period between 1506-1508 Achillini was a Professor at the University of Padua. Achillini taught at Bologna for twenty-eight years, which is longer than anyone who has ever taught at Bologna in medicine or philosophy. 
The University of Padua had a statute, that if a professor failed to read on any assigned day, or failed to have a certain number students it would be documented and then later there would be a diminution of salary per occurrence. During the months of December–March of 1506-1507 Achillini did not meet the requirement for reading, to which he was penalized 351 Bolognese Lire. Achillini also received two strongly-worded letters in August and September of 1507 from the Commune of Bologna stating that his absence was unauthorized, and if it continued he would be penalized severely (500 ducats of gold for the first offense).
Achillini attended many doctoral committees as a member for the examination and approval of candidates. There are records of him attending at least ninety times to these proceedings. The proceedings are doctoral examinations or elections of new members to the Company of Collegiate Doctors.
In addition, Achillini’s was well versed in theology. His initial designs indicate an interest in entering the priesthood. He appears to have begun his seminar studies prior to 1476; the year he entered the tonsure at the Cathedral of Bologna. And though he later shifted his focus to academia, he remained an active theologian throughout his life and contributed to two General Congresses of the Franciscan Order; one in Bologna in 1494 and another held in Rome between 1505 and 1506.
While in residence at Bologna, Achillini is credited as being instrumental in generating interest in William of Ockham . The extent of Achillini’s endorsement is difficult to discern, but it is believed he and his contemporaries at the university instigated a brief Ockhamistic revival as reflected by his students' later works.
The “Anatomical Notes by the Great Alexander Achillinus of Bologna” demonstrate a detailed description of the human body. Achillini compares what he has found during his dissections to what others like Galen and Avicenna have found and notes their similarities and differences. Achillinus states there are seven features when examining the body instead of the believed six given in Galen’s book On Sects. These seven features are size, number, location, form, substance as in thin or thick, substance as in fleshy or bony, and complexion. In this work, Achillinus also gives directions as how to proceed with certain dissections and procedures such as castration, extraction of stone, and removal of the rib cage to further examine the heart and lungs.
He was also distinguished as an anatomist, among his writings being De humani corporis anatomia (Venice, 1516–1524), and Annotationes anatomicae (Bologna, 1520). Achillini's Annotationes Anatomicae was first published by his brother, Giovanni Filoteo, on September 24, 1520. It was published in a small format of eighteen folios with a pair of poems of six and two lines each.
- Lind, L. R. (1975). "Studies in Pre-Vesalian Anatomy: Biography, Translations, Documents". The American Philosophical Society 1: 23–41. See pp. 24-25.
- Matsen, Herbert (1968). "Alessandro Achillini (1463-1512) as professor of philosophy in the "Studio" of Padua (1506-1508)". Quaderni per la storia dell' Università di padova 1: 91–109. See pp. 91-92.
- Matsen, Herbert (1968). "Alessandro Achillini (1463-1512) as professor of philosophy in the "Studio" of Padua (1506-1508)". Quaderni per la storia dell' Università di padova 1: 91–109. See p. 94.
- Matsen, Herbert (1968). "Alessandro Achillini (1463-1513) as professor of philosophy in the "Studio" of Padua (1506-1508)". Quaderni per la storia dell' Universita di padova 1: 91–109. See p. 92.
- Matsen, Herbert (1975). "Alessandro Achillini (1463-1512) and 'Ockhamism' at Bologna (1490-1500)". Journal of the History of Philosophy 13 (4): 437–451.
- Achillini, Alessandro (1975). "Anatomical Notes by the Great Alexander Achillinus of Bologna". In Lind, L. R. Studies in Pre-Vesalian Anatomy: Biography, Translations, Documents. Independence Square Philadelphia: The American Philosophical Society. pp. 42–65.
This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Achillini, Alessandro". Encyclopædia Britannica 1 (11th ed.). Cambridge University Press. p. 144.
- Franceschini, Pietro (1970). "Achillini, Alessandro". Dictionary of Scientific Biography 1. New York: Charles Scribner's Sons. pp. 46–47. ISBN 0-684-10114-9.
- Herbert Stanley Matsen. Alessandro Achillini (1463–1512) and his doctrine of universals and transcendentals: a study in Renaissance ockhamism. Lewisburg, Bucknell University Press 1974
- Online Galleries, History of Science Collections, University of Oklahoma Libraries High resolution images of works by and/or portraits of Alessandro Achillini in .jpg and .tiff format.