The UPCI's understanding of God is strictly monotheistic: there is one God who is absolutely one in person as well as in nature. The UPCI explicitly rejects the idea that God exists as three co-equal, co-eternal persons. Instead, the one God — who is Spirit, omnipotent, omniscient, omnipresent, and eternal — reveals himself in different modes or manifestations: as Father in creation and covenant, as Son in the incarnation, and as Holy Spirit in his work among believers.

Jesus Christ is understood as the fullness of this one God manifested in bodily form. Colossians 2:9 is central: 'in him the whole fullness of deity dwells bodily.' There is no God apart from or alongside Jesus — Jesus is the name that fully identifies and reveals the one God. The UPCI's God is therefore not the God of Trinitarian Christianity (three persons, one substance) but the God of radical biblical monotheism, understood as finding his complete human expression in the incarnate Jesus Christ.

This theology has deep implications for worship and prayer: UPCI believers pray 'in Jesus' name' not as a formula for addressing the Father through the Son, but as the invocation of the one God whose complete name and identity is Jesus. The UPCI's worship is thus strictly Christocentric in a way that goes beyond even high Christology within Trinitarianism.