Symonds was born in 1816 as the youngest son of the family. His father was Sir William Symonds. On the recommendation of Lord Normanby, he joined the survey department in New South Wales in 1839. He moved on to Auckland, New Zealand in 1841 to join his elder brother William Cornwallis Symonds, but his brother drowned in a boating accident in November of that year. For a while, he was acting protector of aborigines, and was in charge of purchase of land from Māori, and the survey of that land. In 1844, he purchased the Otago block with Frederick Tuckett on behalf of the New Zealand Company.
In 1846, he became private secretary to Governor George Grey. The governor transferred an island in the Firth of Thames to Symonds to create a test case regarding the Crown's pre-emptive right of purchase to Māori land deriving from the Treaty of Waitangi; in R v Symonds, the court decided in favour of the Crown's case. In 1847, he was one of the founding members of the Auckland Savings Bank. He returned to England for some time, where he married in 1849. He came back to New Zealand in 1849 in charge of a detachment of the Fencibles, which he settled in Onehunga. He became a justice of the peace in 1853, was appointed Native Secretary in 1855, and became Onehunga's resident magistrate and returning officer in 1856.
He resigned from those roles when he was elected to represent the Pensioner Settlements electorate from 1858 to 1860, when he retired. In 1861, he was again appointed Resident Magistrate. He was a judge of the Native Land Court from 1862 to his retirement in 1882.
Symonds died suddenly on 3 January 1883. He was ill for only half an hour and in the beginning did not think it necessary to call for his son-in-law, who was a doctor. He was survived by his wife, four daughters, and one son. His wife (Alethia Seymour, née Wilson) died in November 1898.