He was probably born in the Holy Roman Empire at Cologne about 1270 and probably died at Toledo, then in the Kingdom of Castile, in 1340.

[1][2][3] He was the third son of the Asher ben Jehiel (known as the "Rosh"), a rabbi of the Holy Roman Empire who, in 1303, moved to Toledo in Castile, due to increasing persecution of Jews in his native Germany.

Besides his father, who was his principal teacher, Jacob quotes very often in the Turim his elder brother Jehiel; once his brother Judah[4] and once his uncle Chaim.

[5] Some say Jacob succeeded his father as the rabbi of the Jewish community of Toledo (Zacuto), while others say his brother Judah ben Asher did.

He lived in abject poverty most of his life, and according to the Sephardic Community of Chios, is said to have fallen ill and died with his ten companions on the island of Chios, in Greece, whilst travelling.