Aristotle’s authorship of the Magna Moralia (MM) as well as the date of the treatise remain debatable among scholars, with the majority opting for its post-Aristotelian and early Hellenistic character. A few scholars who defend Aristotelian authorship either treat it as an early treatise written during Aristotle’s first Athenian period when he was a member of Plato’s Academy (before 348 BC) or assign it to the Macedonian period while at the same time finding traces of a later editor to whom they ascribe the Ionisms typical of the koine and/or certain historical examples in the text which they treat as anachronisms for the date before 335/334 BC, i. e. Aristotle’s return to Athens (sometimes these additions are ascribed to Aristotle himself). However, there are no compelling reasons for a date as early as the first Athenian period, and the MM on the whole exhibits a homogeneity of style, betraying no revision; on the other hand, the Ionisms occur in the doubtless genuine works of Aristotle, even if to a lesser extent. It is shown in the paper that none of the examples in the MM imply a date later than 335/334 BC. There is also indication of an approximate date for the treatise: the mention of Mentor — a powerful mercenary commander under Artaxerxes III, who was guilty of capturing and later executing Hermias of Atarneus, Aristotle’s friend and benefactor — expresses the judgment of a person contemporary to these events (“Mentor seemed to be clever, but he was not prudent,” I. 34. 1197 b 18–26) rather than a later redactor or compiler. It is tempting to suppose that the remark comes from Aristotle himself and that it was made after Hermias’ and probably soon after Mentor’s own death, i. e. between 340 and 336 BC. Granted that the MM, as most scholars agree, has a more primitive character than the Eudemean Ethics and the Nicomachean Ethics and, if genuine, should be dated earlier than both of these, the MM could have been written during Aristotle’s sojourn in Macedonia, before his return to Athens. One may also suppose (with F. Dirlmeier) that the MM reflects his genuine spoken manner, which was otherwise polished in lecture courses and written for the Athenian audience. This might explain the extraordinary quantity of Ionisms in the MM: it would have been natural to pay less attention to Attic purity in Macedonia where the spoken language of the educated people was in all probability Attic, with some mixture of Ionisms, and which corresponds to Aristotle’s own original manner of speaking as a native of Stagira.