Oneness Pentecostals categorically reject the doctrine of the Trinity. The UPCI's Articles of Faith declare that 'the one true God' is 'an omnipotent, omniscient, and omnipresent Spirit' who is 'absolutely one' — not three persons. The designations Father, Son, and Holy Spirit are understood as names, titles, or roles that the one God assumes in relation to creation and redemption, not as references to three distinct divine persons who share one divine essence.

In Oneness theology, Jesus Christ is identified as the full and complete manifestation of the one God in human flesh. The name 'Jesus' is understood as the complete redemptive name that encompasses Father, Son, and Holy Spirit. Colossians 2:9 ('in him the whole fullness of deity dwells bodily') is a central Oneness proof text: Jesus is not one of three divine persons but the one God incarnate in totality. When Jesus prayed to the Father, he was the Son (his human nature) addressing the Father (the divine nature within him), not a second divine person addressing a first.

This theological position places Oneness Pentecostals outside Trinitarian Christianity and in tension with both mainline Trinitarian Pentecostalism (like the Assemblies of God) and historic Christian orthodoxy. The Assemblies of God formally separated from Oneness Pentecostals in 1916, requiring Trinitarian baptism. Oneness Pentecostals regard the Trinity as a 4th-century corruption of biblical monotheism and see themselves as recovering the apostolic understanding of God as fully revealed in Jesus.