Ansdell, son of a Liverpool artisan, entered the Liverpool Academy Schools in 1835, where he was later elected President (1845-46). In 1840 he exhibited Shooting Party in the Highlands (Walker Art Gallery, Liverpool), one of many highland subjects that he painted and the first of 149 works exhibited at the Royal Academy, London, between 1840 and his death in 1885. He was elected an Academician in 1870 and also exhibited at the British Institution between 1846 and 1865.
During the course of his extremely successful career, Ansdell collaborated with several other artists, including John Philip with whom he travelled to Spain, William Powell Smith and Thomas Creswick. His patrons included the Earl of Sefton, for whom he painted The Waterloo Cup Coursing Meeting (1840, Walker Art Gallery, Liverpool), the Earl of Derby, Earl Spencer and the Marquess of Bute.
His settings are often inspired by northern landscapes; he spent a great deal of time in a lodge on Loch Laggan and in 1861 built a large house and studio called Starr Hills outside Lytham. His focus on Scottish subjects reflects the growing popularity of the Highlands. Sir Walter Scott was partially responsible for encouraging this romantic interest in Scotland, many of his novels had highland settings and were peopled by clans, chieftains, ghillies and crofters. Queen Victoria made frequent visits to Scotland, in 1853, purchasing the estate of Balmoral in 1853. One of her favourite artists, Sir Edwin Landseer (1802-1873), had established his reputation with his paintings of highland sports and subjects. Ansdell's animal subjects often rival those of his great contemporary, Landseer, both in the variety of his subject matter and details and accurancy of their execution.
Ansdell continued painting until his death in 1885 at Collingwood Tower, Farnborough, Hampshire. The contents of his studio were sold at Christie's, London, on 19 and 20 March 1886.