Holroyd was the son of a London merchant. He was initially educated at Ripon Grammar School and then took medical degrees at the University of Edinburgh and Christ's College, Cambridge. After practicing as a physician in London for a short period he entered Lincoln's Inn and was called to the bar. While studying law he traveled extensively in the Middle East, became proficient in Arabic and was the first Englishman to visit Kurdufan. He exposed the continuing horrors of the slave-trade in Sudan. Holroyd emigrated to the antipodes in 1843 and commenced practice as a solicitor and barrister. Holroyd was a master in equity of the New South Wales Supreme Court between 1866 and 1881 and an acting justice in 1879. While on the bench, he was accused of displaying "extraordinary behaviour" but this was considered to be a product of his short temper rather than evidence of misconduct. Holroyd was an alderman and the first mayor of Prospect and Sherwood Municipal Council, a leading Freemason and a trustee of Sydney Grammar School and St. Paul's College, Sydney. He developed a large property called "Sherwood Scrubs" in the area. The former local government area of Holroyd City Council and the suburb therein also called Holroyd, were named in his honor in 1927. His property there "Merrylands" also gives its name to the suburb of that name.
Colonial Parliament
In 1851, prior to the establishment of responsible self-government, Holroyd was elected to the semi-elective Legislative Council. He represented the electorate of Western Boroughs until the granting of responsible self-government in 1856. Subsequently, at the first election under the new constitution he was elected to the Legislative Assembly as the member for the same seat. He was defeated by 6 votes at the next election in 1858. Holroyd re-entered parliament as one of the two members for Parramatta at an 1861 by-election caused by the resignation of James Byrnes. However, Byrnes defeated him at the subsequentgeneral election. He then retired from political life.
Government
Holroyd was the Secretary for Public Works in the first government of James Martin. He held this position for 15 months but resigned after being accused by William Arnold of accepting a bribe to appoint an associate to the bench of magistrates. A parliamentary commission found no truth in this accusation.
