We know of only a small number of philosophical or scientific translations from Arabic to Hebrew that were certainly produced in Christian Spain in the thirteenth and fourteenth centuries. An anonymous translation of Archimedes’ The Measurement of the Circle (referred to by Tony Lévy as HA) may have been produced in fourteenth-century Castile by Alfonso, the author of Sefer Meyaššer ʿaqov (henceforth SMA)— identified by Gita Gluskina, and subsequently by Gad Freudenthal, as Alfonso of Valladolid, the Jewish apostate otherwise known as Abner of Burgos. A comparison of translation HA of Archimedes and the original mathematical treatise SMA strongly suggests, but does not conclusively prove, that they are by the same hand. It is shown that Alfonso had a good command of Arabic and studied mathematics and probably also philosophy from Arabic sources. There is no decisive piece evidence that he was acquainted with any of the Hebrew translations of either mathematical or philosophical texts produced in Provence in the thirteenth and first half of the fourteenth century. Abner of Burgos was known as an erudite scholar who was a central figure in Jewish intellectual life in Castile before his conversion. If he was indeed the author of SMA and the translator of The Measurement of the Circle, we may conjecture that Castilian Jews of the first half of the fourteenth century had scant exposure to the translations of Greek and Arabic authors by their Provençal coreligionists. This situation gradually changed in the second half of the century.