In 1834, he went to Europe, leaving his mother well provided for, and remained abroad sixteen years during which he studied with Antoine-Jean Gros in Paris and in Rome, came under the influence of Thomas Couture, and painted assiduously.

He won a second-class medal in Paris in 1855, when he exhibited his Franklin Urging the Claims of the American Colonies Before Louis XVI.

[2] In 1855, he returned to the United States, establishing his home and studio in Chicago, Illinois, where he remained based for the next 14 years until 1869.

[3] Healy also partnered with Bryan, as well as William Butler Ogden, Sidney Sawyer, and Edwin H Sheldon, in founding Graceland Cemetery.

Healy went back to Europe in 1869, painting steadily, chiefly in Rome and Paris, for twenty-one years.

His style, essentially French, was sound, his color fine, his drawing correct and his management of light and shade excellent.

Among his portraits of eminent persons are those of Daniel Webster, Henry Clay, John Calhoun, Pope Pius IX, Arnold Henry Guyot, William H. Seward, Louis Philippe, Marshal Soult, Hawthorne, Prescott, Longfellow, Liszt, Gambetta, Thiers, Lord Lyons, Sallie Ward and the Princess (later the queen) of Romania.

In one large historical work, Webster's Reply to Hayne (1851; in Faneuil Hall, Boston), there are one hundred and thirty portraits.