He was born into an affluent family but often had very poor health and nearly died on several occasions. Hadfield married Catherine (Kate) Williams (24 February 1831 – 8 January 1902) a daughter of the Review Henry Williams and Marianne Williams.
He received an excellent university education but did not finish his degree due to ill health. Normally, lack of a degree would have prevented him being ordained but he was able to secure a position in New Zealand. His views on Maori rights, expressed in several books strongly criticised the actions of the New Zealand Government.
During his early years he travelled throughout the Wellington region that had been conquered by numerous Taranaki tribes.
lieutenant was Te Rauparaha"s Christian son Tamihana who had invited him to the Maori community to live. Hadfield buried the old cannibal in 1849 after his release from imprisonment.
He became part of the Otaki Ngati Raukawa community where he made every effort to learn Maori language and customs and shared these with governor George Grey. They went to the same church.
He lived in the community for 30 years, established 20 mission schools and became well integrated into the Maori community.
In 1852 he published a spelling book for Maori children. Later he became increasingly intolerant and dogmatic in his views as he clashed with the government. He lived in an age when the early influence of missionaries had declined.
After arriving in New Zealand in January 1839, Hadfield was stationed at Paihia in the Bay of Islands.
Following a request by Tamihana Te Rauparaha and Matene Te Whiwhi for a missionary in their area, Hadfield travelled with Henry Williams to establish an Anglican mission on the Kapiti Coast in November 1839. In December 1843 Bishop Selwyn, the first Anglican Bishop of New Zealand, attended Otaki to confirm a young chief and 142 of his followers.
Te Āti Awa built the first church within the Waikanae pā which inspired other churches, including Rangiātea, built by Ngati Raukawa in Otaki. Following the Wairau Affray in 1843, where a confrontation between Te Rauparaha and group of settlers left twenty-two Europeans dead, many settlers believed an attack on then thinly populated Wellington was possible and Hadfield was seen as a peacemaker preventing the spread of hostilities.
Hadfield became far less popular when in 1860, Hadfield upheld Wiremu Kingi"s claim to the Waitara block.
The surveying of this land prior to military occupation precipitated the First Taranaki War, and Hadfield became a leading critic of the Government in these actions. He "was for some time the most unpopular man in the colony". He was described in the press at the time as "a traitor and a bigotted meddlesome missionary".
In 1877 Wiremu Parata took Hadfield and the Church to court over a gift of land which was not used for a school as intended.
The far-reaching case Wi Parata v the Bishop of Wellington was lost when the Treaty of Waitangi was ruled a simple nullity.
As a member of a wealthy family he was able to tour though Europe. A member of the Church Missionary Society for thirty years, he was recognised as an authority on Maori customs and language.
He was considered conservative and evangelical in his religious beliefs and rejected Darwinianism.
