The Bible does not say how the apostle Paul died. Writing in 2 Timothy 4:6–8, Paul seems to be anticipating his soon demise: “For I am already being poured out as a drink offering, and the time of my departure has come. I have fought the good fight, I have finished the race, I have kept the faith. Henceforth there is laid up for me the crown of righteousness, which the Lord, the righteous judge, will award to me on that Day, and not only to me but also to all who have loved his appearing.”
Second Timothy was written during Paul’s second Roman imprisonment in AD 64—67. There are a few different Christian traditions in regards to how Paul died, but the most commonly accepted one comes from the writings of Eusebius, an early church historian. Eusebius claimed that Paul was beheaded at the order of the Roman emperor Nero or one of his subordinates. Paul’s martyrdom occurred shortly after much of Rome burned in a fire—an event that Nero blamed on the Christians.
It is possible that the apostle Peter was martyred around the same time, during this period of early persecution of Christians. The tradition is that Peter was crucified upside down and that Paul was beheaded due to the fact that Paul was a Roman citizen (Acts 22:28), and Roman citizens were normally exempt from crucifixion.
The accuracy of this tradition is impossible to gauge. Again, the Bible does not record how Paul died, so there is no way to be certain regarding the circumstances of his death. But, from all indications, he died for his faith. We know he was ready to die for Christ (Acts 21:13), and Jesus had predicted that Paul would suffer much for the name of Christ (Acts 9:16). Based on what the Book of Acts records of Paul’s life, we can assume he died declaring the gospel of Christ, spending his last breath as a witness to the truth that sets men free (John 8:32).