Born on 12 February 1818 into an Anglican family at Stutton, Suffolk he had the advantage of a good education. He became a local preacher and offered for missionary service in 1839. He went out to New Zealand on the Triton as a single man with the group of missionaries for the South Pacific led by John Waterhouse. Arriving in May 1840, he spent a few months at Kawhia and then went south to be the first resident missionary at Wellington. His responsibilities were to minister to the Maori in the Port Nicholson area, to extend the boundaries of the mission field and to care for the colonists. Ill-health dogged him there and elsewhere for some years, and the lack of a partner did not help his ministry.
In Wellington he was confronted by problems over the Mission's land claim. He had to live in a native-style house, and his predicament led to visits by his senior colleagues James Wallis and John Whiteley. Wallis commended Aldred for his work, though he had earned the dislike of some Europeans by his opposition to the liquor trade. When Whiteley visited, Aldred was visiting the Chatham Islands, the first missionary to do so.In 1843 he went to Nelson to open the work there with both Europeans and Maori. All the Wesleyan natives on the south side of Cook's Strait were under his care; there were large numbers at both Motueka and D'Urville Island. A church for the settler Methodists was opened in 1845 and he held services at a number of other places. He remained in Nelson until 1849, but twice wrote to the Committee in London seeking their permission to return home in order to find a wife. He was a concern to the new General Superintendent, Walter Lawry.Appointed to Wellington as assistant minister to James Watkin in 1849, he was the first resident minister in the Hutt Valley. Shortly afterwards he travelled to Auckland, where on 1 May 1849 he married Mary Australia, the youngest daughter of Lawry, at the High Street Chapel. As Lawry's son-in-law he became embroiled in the dissension that led a majority of the missionaries to complain to London about their Superintendent.At a later stage Aldred refused to go to Christchurch to open a new cause until he had received a clear directive from London. However, he did serve there from 1854 until 1860, working largely among the new settlers. The first church was opened immediately after his arrival. His work with the Maori was confined to a fairly small group living at Kaiapoi and to those around the Akaroa Peninsula and Lyttelton Harbour. The registers show that Maori from as far south as Moeraki and as far north as Kaikoura came to him for baptisms and weddings.After four years in Wellington, 1860-1864, he was sent to Dunedin, where a society with a resident minister had been established in 1862. Aldred remained there until 1867, when, because of ill health following an accident, he received permission to superannuate. He lived out a long and active retirement in Christchurch, acting as secretary of the Canterbury District for 25 years and being much involved in the British and Foreign Bible Society. He had a reputation as a Maori scholar and an expert in Maori land tenure, and was frequently used as an interpreter in land claims. He died at Christchurch on 14 January 1894. All comments about him refer to his gentle and unobtrusive nature, with his health being a constant problem. Though remembered as a diligent pastor, he seems not to have been an initiator. This may account for the fact that all his appointments were to developing townships rather than to the more primitive mission stations.