Can Christians be demonized? Simply put, yes. The Bible does not have a lot to say about it Christians having demons, but there are definite hints of it. Here are just a few of them.
First, Peter in Mark 8:33 tries to stop Jesus from going to Jerusalem to suffer and die. Jesus rebukes him, calling him, “Satan,” and that his mind is not on the things of God.
Next, Ananias in Acts 5:3 is said to have had Satan fill his heart.
Third, Paul says in 2 Timothy 2:26 that Christian leaders (those opposing Timothy) can be trapped and held captive to the devil to do his will.
There are many other places in the Bible where believers are referred to as “deceived” and we know that the devil is a liar.
Something to note about demonization is that it refers to a range of influence and/or attack. Simply put, the worst type (possession) is either impossible or very unlikely to affect people who are baptized with water and the Holy Spirit. However, harassment or oppression are definitely possible for Christians.