This is at the heart of all we say and do. We believe in:

• The One true God who lives eternally in three persons, the Father, the Son and the Holy Spirit.
• The love, grace and sovereignty of God in creating, sustaining, ruling, redeeming and judging the world.
• The divine inspiration and supreme authority of the Old and New Testament Scriptures, which are the written Word of God – fully trustworthy for faith and conduct.
• The dignity of all people, made male and female in God’s image to love, be holy and care for creation, yet corrupted by sin which incurs divine wrath and judgement.
• The incarnation of God’s eternal Son, our Lord Jesus Christ; born of a virgin birth.  He was truly divine and truly human, yet without sin.
• The atoning sacrifice of Christ on the cross; dying in our place, paying the price for sin and defeating evil, so reconciled with God.
• The bodily resurrection of Christ, the first fruits of our resurrection; His ascension to the Father and His reign and mediation as the only Saviour of the world.
• The justification of sinner solely by the grace of God through faith in Christ.
• The ministry of God the Holy Spirit who leads us to repentance, unites us with Christ through new birth, empowers our discipleship and enables our witness.
• The church, the body of Christ, both locally and universally.
• The priesthood of all believers – given life by the Holy Spirit and endowed with the Spirits gifts to worship God and proclaim the gospel, promoting justice and love.
• The personal and visible return of Jesus Christ to  fulfil the purposes of God, who will raise all people to judgement, bringing eternal life to the redeemed and eternal condemnation to the lost, and establish a new heaven and earth.
  

Siloam Baptist Church opened on the Llanrumney Estate on 21 May 1958.

The Rev. James Thomas, President of the Cardiff Baptist Union, was quoted in the local paper as saying, "The Baptist Union had been continually trying to keep in touch with the floating population and we feel there is just as much need for a church on this estate as anywhere else. ... This is the Lord's doing and it is marvellous in our eyes. To Him the Glory."

The paper also reported, "Some time ago, 'Siloam' Chapel in the dockland area of Cardiff was closed down owing to the decline in the population, and in giving the new Church the same name, it is felt the spirit of the old church has been transferred to Llanrumney."

A week later, the first woman pastor in Cardiff was inducted as Siloam's first pastor. Eileen Gane, who was 26 at the time, had thought to become a missionary but decided "that she could do more valuable work at home."