Is it possible for a person to believe in some way and yet not be saved?

TL;DR:

Someone can “believe” in Jesus in a superficial way yet not be truly saved, as genuine salvation requires trusting Him with the heart, not just the mind. But those who genuinely place their faith in Christ are eternally secure in God’s hand, and nothing can separate them from Him.

what does the bible say?

Although people may pay lip-service to Jesus or may even be involved in ministry, this doesn’t equal a genuine relationship with Jesus. While some may acknowledge Jesus’ existence, they have no genuine relationship with Him, so they haven’t been born again (Matthew 7:21-23). In Matthew 13, Jesus tells the Parable of the Sower to teach about those who may have initially responded positively to the gospel, but were never truly saved, similar to Judas Iscariot. This initial receiving but later rejecting of Jesus also seems to be apparent in some of His “followers” in John 6. We cannot earn our salvation (Ephesians 2:8-9) nor are there multiple ways to get saved; only through Jesus Christ can we receive salvation (John 14:6; Acts 4:12). Similarly, we must understand that believing in Jesus’ existence isn’t enough to receive salvation (Romans 1:20; James 2:19). To truly believe in Christ starts with realizing we are sinful and in need of our Savior (Romans 3:23, 6:23). We must then put our faith in Jesus Christ as laid out in Romans 10:9: "if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved." No religious rite or “good work” can save us; only Christ saves, and He will not forsake His true followers (John 10:27-30).

from the old testament

Deuteronomy 6:5 identifies the foundation of all belief: “You shall love the Lord your God with all your heart and with all your soul and with all your might” Jesus would later call this the “great and first commandment” in Matthew 22:38. Loving the Lord means putting our faith and trust in Him; salvation is based on that.
Through the prophet Isaiah, the Lord chastised those whose heart was absent from their religious observance: “. . . this people draw near with their mouth and honor me with their lips, while their hearts are far from me” (Isaiah 29:13). Salvation involves trust in Lord, not merely saying the right words.

from the new testament

Matthew 7:21-23 has been misinterpreted to suggest salvation can be lost, but Jesus isn’t saying we must work to maintain salvation or that we can lose it. The people mentioned in this passage are those He never knew in the first place.
Jesus presents the parable of the sower in Matthew 13. Arguably, Judas, Jesus’ disciple who later betrayed Him, was a real-life manifestation of this. Judas merely followed Jesus, yet seemingly did not believe in Him.
In John 6 many of Jesus’ followers left when He presented them with a challenging reality about following Him.
The only means of salvation is through Jesus Christ (John 14:6; Acts 4:12).
In John 10:27-30, Jesus says, “My sheep hear my voice, and I know them, and they follow me. I give them eternal life, and they will never perish, and no one will snatch them out of my hand. My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father 's hand. I and the Father are one." This passage makes it clear that if we are a genuine believer in Christ, there is no way we cannot be saved—-we are forever secured in Jesus Christ and our Heavenly Father.
God’s existence is evident to everyone (Romans 1:20) but merely acknowledging this is insufficient for salvation. True belief goes beyond just acknowledgement.
To be saved, must place their faith in the God of the Bible and recognize we have all sinned and are deserving of punishment (Romans 3:23, 6:23).
Romans 10:9 clearly lets us know how we can be saved.
Scripture teaches that we cannot save ourselves (Ephesians 2:8-9).
James 2:19 says, "You believe that God is one; you do well. Even the demons believe—and shudder!" Believing that God exists is not saving faith.

implications for today

Faith implies not only intellectual assent, but action. The illustration of a chair is commonly used. To truly have faith in a chair, one must sit in it. A person can "believe" that the chair will support their weight. They may even recognize they have a need to be supported by the chair. But they do not exercise faith until they actually sit in the chair.

Similarly, someone can "believe" without actually being saved. Salvation is by God's grace alone and received through faith. Faith implies some action on our part, but this cannot be a reason for us to boast, for it is by God's grace alone that we can be saved. Moreover, belief in salvation transforms us. It isn't an intellectual agreement only, but a recognition of our hopelessness apart from God and His gracious offer to save us. Then we act on that belief by putting our faith in Jesus. As a result, we are born again, brought into a reconciled relationship with God, given the indwelling Holy Spirit, and our lives are changed forever (Romans 8:29-30; Ephesians 1:3-14, 2:16-22, 4:17-24; Philippians 1:6; 2:12-13; 1 Peter 1:3-9, 13-25).

understand

Someone might intellectually accept God’s existence, yet not be saved because they haven’t given their heart to the Lord.
Some may appear to be saved yet be far from Christ.
Those who are genuinely saved cannot lose their salvation.

reflect

How do you distinguish your intellectual assent to Christ from your salvific assent?
How does the Holy Spirit assure you of your salvation?
In what way is your everyday walk with the Lord impacted by knowing that you cannot lose your salvation?

engage

How can the church reach those who say they “believe” in God but whose life doesn’t reflect a saving faith in Him?
What are some signs that one is merely a professing believer rather than a genuinely saved believer?
How can believers emphasize love for the Lord in their outreach to unbelievers?