Most people know that Paul was a pious Jew, a former Pharisee trained alongside other Jewish sages at the feet of Gamaliel (Acts 22:3). Many New Testament readers also see Paul as a radical convert to Christianity, but he never actually called himself a Christian.
Defending himself before the procurator Felix, Paul states, “I admit to you, that according to the Way which they call a sect I do serve the God of our fathers, believing everything that is in accordance with the Torah and that is written in the Prophets” (Acts 24:14). Standing before another council, Paul identified himself as “a Pharisee, son of Pharisees” in the present tense (Acts 23:6). Defending himself before King Agrippa, Paul insisted that he always “lived as a Pharisee” (Acts 26:5). What is amazing is that all these words were spoken after his encounter with the risen Christ, not before!
Of course, Paul was a follower of Christ. There is no dispute. But he chose to identify himself over and over as a Jew of Pharisaic persuasion. In its earliest form, the term Χριστιᾱνός (“Christian” or “Christ-follower”” was a politically-loaded term, affirming one’s loyalty to the Jewish Christ, rather than to the Emperor or the gods of Rome. This means that, in the first century, to be a “Christian” meant affiliation with something intrinsically Jewish.
So, was Paul a Christian? It’s a complicated question. As a Jew, Paul’s loyalty was clear and he did not need another name to show his belonging to the Jewish Christ. For Paul, being a Jew and a Pharisee who followed the Messiah Jesus was enough.