Many societies in the Kairuku-Hiri district have very strong traditional beliefs and practices. However, the adoption of christianity has had such great impact that most of these traditional/cultural values have rapidly been converted. More than 95% of the population are followers of the Christian faith now. In some remote areas, traditional customs may still be practised where for example, social harmony is ethnically maintained through the chieftain system.

The influx of missionaries in the 1880s and 1890s introduced and promoted better education, health, welfare and transportation. In fact, the history of religion and churches dates back to the late 19th century when the first mission work was launched in Papua New Guinea. The missionaries brought with them the 'Good News' of the Gospel and changed the cultural and religious practices that were found to be inappropriate.

The Bible Society of PNG, established in 1955, is a registered non-profit organisation that represents all Christian denominations in the country. It is involved in producing and publishing bible stories and translations with the help of other translation organisations like the Bible Translators Association (BTA), Summer Institute of Linguistics (SIL), Churches, Christian Bookshops and volunteers. The first bible translation was the Motu gospel in 1881 and now there are five translations in Hiri Motu, Koiari, Roro, Mekeo and Koitabu dialects for Kairuku-Hiri people.

The majority of the coastal areas along Kairuku and Hiri districts are predominantly United Church with the hinterland in the Koiari areas dominated by the Seventh Day Adventist (SDA). Most of inland Kairuku areas are mainly Roman Catholics, which is the largest in the country. Also present in increasing numbers are other denominations such as Evangelical Lutheran, Baptist, Church of Christ, Orthodox, Presbyterian, Protestant, Jehovah Witness, Salvation Army, Bahai and the Pentecostals i.e. CLC, CRC, AOG.

Churches have always played a significant role in every society where everybody is part and partial of the work that it carries out. Many churches, especially the Catholic Church, manage educational institutions that have been operating since the 1800s and have produced prominent and respected leaders in the community and the country as a whole. Church related activities and events like the synod, boubou, youth rallies, crusades, easter camps, new church buildings, and pastoral ordination are regarded as imperative and therefore many christians invest their time and money in order to generate fruitful and successful results for the extension of the kingdom of God.