Did Boethius write in Classical, Late, or Medieval Latin? His style does not appear medieval in the Peter of Spain sense of Medieval Latin; however, it does not appear to be classical in the Ciceronian sense of Classical Latin. Hence, it seems he might be best classified as a writer in the nebulous Late Latin, but the classification "Late Latin" is not commonly accepted. If Late Latin is rejected as a distinct style of Latin, would he be classified as writing in a mixed Classical-Medieval style?
In Medieval Latin, K. P. Harrington briefly describes the style of Boethius (480–524) in his chapter entitled "The Rise of Late Latin":
The sort of straightforward prose writing that had dominated philosophical and even theological discourse for centuries in Greek and, to a much lesser extent, in Latin was challenged by Late Latin writers of the so-called mixed style, like Boethius, who put to the test the old allegiances of a rational prose set against a poetry grounded in the passions of the heart. [...] The Christian outlook, then, privileged a view of the world that discounted, at least by antique terms, hard and fast categories of reason and emotion—a view championed by Boethius and carried forward in several later works of the Medieval Latin tradition.
Boethius also introduces a number of elements of the Greek language in his translations into Latin of classic Greek works, another aspect of "Late Latin" as described by Harrington. These developments made the language more suitable for theological use, as in the writings of Pope Gregory I (540–604).
So according to Harrington, Boethius could certainly be described as a Late Latin writer who played an important part in the development of Medieval Latin.