Egan was born in Windsor, New South Wales and was a foreman at the Government Dockyards, Sydney from 1824 to its closure in 1835. He then went into Business and acquired several trading vessels but went bankrupt in 1843 and later became a wine and spirit merchant. He became an alderman of the Sydney City Council on its creation in 1842, rising to mayor in 1853. He purchased two 40-acre (16 ha) blocks of land in Beacon Hill in 1857.
Egan was elected to the Legislative Council on 1 April 1854, representing the Pastoral District of Maneroo. In April 1856 he was elected at the first election to the Legislative Assembly, representing Maneroo, which was renamed Monaro in 1858. From 1859 to 1869 he represented Eden and from 1870 to his death he represented Monaro. From 27 October 1868 until his death he was the Postmaster-General of New South Wales.