In Oneness Pentecostal theology, the Holy Spirit is not a distinct third person of the Trinity but the one God himself acting and dwelling in believers. 'Holy Spirit' is a description of God's nature and mode of operation, not the name of a separate divine person. When the New Testament speaks of the Spirit dwelling in believers, it is the same God — the same divine being fully manifest in Jesus — who is present with and in the community of faith.

Despite this non-Trinitarian pneumatology, the UPCI places enormous emphasis on the experience of Spirit baptism — and it is precisely this Spirit baptism that is one of the three required elements of the new birth (Acts 2:38). The initial physical evidence of receiving the Holy Spirit is speaking in other tongues, consistent with the UPCI's Pentecostal heritage. This experience of the Spirit is regarded as essential, life-transforming, and accessible to all believers.

The tension between the UPCI's non-Trinitarian theology (the Spirit is not a separate person) and its intense experiential emphasis on Spirit baptism (the Spirit is given, received, and evidenced by tongues) is a distinctive feature of Oneness Pentecostalism. The Spirit is understood as the one God making himself present in and through the believer — an intensely personal experience of the divine, even if the divine is understood as strictly unipersonal.