His education was of the plainest kind, but he was eager for culture, fond of reading, and anxious to become an artist. His father, however, placed him, in 1820, in Newenham's Bank, where he remained for two years, and then left to study in the Cork school of art. In 1825 it happened that Sir Walter Scott was travelling in Ireland, and young Maclise, having seen him in a bookseller's shop, made a surreptitious sketch of the great man, which he afterwards lithographed. It was exceedingly popular, and the artist became celebrated enough to receive many commissions for portraits, which he executed, in pencil, with very careful treatment of detail and accessory.
Various influential friends perceived the genius and promise of the lad, and were anxious to furnish him with the means of studying in the metropolis; but with rare independence he refused all aid, and by careful economy saved a sufficient sum to enable him to leave for London. There he made a lucky hit by a sketch of the younger Kean, which, like his portrait of Scott, was lithographed and published. He entered the Academy schools in 1828, and carried off the highest prizes open to the students.
In 1829 he exhibited for the first time in the Royal Academy. Gradually he began to confine himself more exclusively to subject and historical pictures, varied occasionally by portraits of Campbell, Miss Landon, Dickens, and other of his literary friends. In 1833 he exhibited two pictures which greatly increased his reputation, and in 1835 the "Chivalric Vow of the Ladies" and the "Peacock" procured his election as associate of the Academy, of which he became full member in 1840. The years that followed were occupied with a long series of figure pictures, deriving their subjects from history and tradition and from the works of Shakespeare, Goldsmith and Le Sage.
He also designed illustrations for several of Dickens's Christmas books and other works. Between the years 1830 and 1836 he contributed to Fraser's Magazine, under the pseudonym of Alfred Croquis, a remarkable series of portraits of the literary and other celebrities of the time character studies, etched or lithographed in outline, and touched more or less with the emphasis of the caricaturist, which were afterwards published as the Maclise Portrait Gallery (1871).
In 1858 Maclise commenced one of the two great monumental works of his life, the Meeting of Wellington and Blücher, on the walls of Westminster Palace. It was begun in fresco, a process which proved unmanageable. The artist wished to resign the task; but, encouraged by Prince Albert, he studied in Berlin the new method of water-glass painting, and carried out the subject and its companion, the "Death of Nelson", in that medium, completing the latter painting in 1864.
The intense application which he gave to these great historic works, and various circumstances connected with the commission, had a serious effect on the artist's health. He began to shun the company in which he formerly delighted; his old buoyancy of spirits was gone; and when, in 1865, the presidentship of the Academy was offered to him he declined the honor. He died of acute pneumonia on the 25th of April 1870.
His works are distinguished by powerful intellectual and imaginative qualities, but most of them are marred by harsh and dull coloring, by metallic hardness of surface and texture, and by frequent touches of the theatrical in the action and attitudes of the figures. His fame rests most securely on his two greatest works at Westminster.
A memoir of Maclise, by his friend WJ O'Driscoll, was published in 1871.