He frequently collaborated with fellow stage actor Edwin Booth, touring together and achieving immense success.

[3] In December 1856 he made his first New York appearance at the Chambers Street theatre as Sir Thomas Clifford in The Hunchback.

[4] Among his many and varied parts may be mentioned Hamlet, King Lear, Macbeth, Shylock, Richard III, Wolsey, Benedick in Much Ado About Nothing, Richelieu, David Garrick, Hernani, Alfred Evelyn, Lanciotto in George Henry Boker's (1823–1890) Francesca da Rimini, and Janies Harebell in The Man o' Airlie.

Barrett acted in London in 1867, 1882, 1883 and 1884, his "Cardinal Richelieu" portrayal in Edward Bulwer-Lytton's drama being considered his best part.

[4] He was particularly successful in Kansas City, Missouri, where he performed for a week in December 1870 in the inaugural season of the Coates Opera House; he returned 11 times.

[7] In addition to his acting, Barrett also wrote a life of Edwin Forrest in the American Actors Series (Boston, 1881).

That year, after organizing performances starring Booth and Polish actress Helena Modjeska, he traveled to a spa in Germany before rejoining them in the fall.

[12] A few years after his death, author Eugene Field criticized the condition of his grave in Massachusetts, writing: "The neglect with which Barrett's memory has been treated... is one of the most shameful blots upon the theatrical profession.

[16] Barrett was a close friend of George Armstrong Custer and hosted him whenever the cavalry officer visited New York.

At one point the pair reportedly killed a number of the rapidly disappearing animals from the top of a moving train in Kansas.

[17] One critic noted Barrett had "a well knit form and face capable of expressing sorrow, by the merest movement of a muscle; joy by the kindling of the eye; or rage, by the transport of the entire body".