Maybe. He claims to be one in the NT, or at least to have had some Rabbinic background, specifically having studied under Gamliel, a prestigious Rabbi of the 1st Century. He is not, however, referenced in any Jewish texts (though another Rabbinic apostate is), nor does his theological background seem terribly rabbinic. He may've exaggerated his religious credentials in his writing a bit. Ultimately, we have no way of knowing.