He briefly taught at the Washington Seminary during his studies, and after graduating, was a professor for the next thirty years at Holy Cross, Woodstock, and Georgetown University.

He held the position for three years, and spent the remainder of his life teaching and working as a historian of the Catholic Church in the United States and of colonial Maryland.

Devitt's father became active in the North End parish of St. Mary's, which was run by the Jesuits, under the pastorship of John McElroy.

He completed two years there before meeting Burchard Villiger, the provincial superior of the Jesuit Maryland Province, and applied for membership in the order.

[2] While at the novitiate, the American Civil War broke out, and the school was several times commandeered by the armies as a makeshift hospital, the novices and juniors being ordered to tend to the wounded.

[4] He was a professor at the school at the time Abraham Lincoln was assassinated, and he marched with the Gonzaga students in the deceased president's funeral procession.

Eventually, on September 3, 1891, Devitt's status was changed to rector and president of Boston College by the Jesuit Superior General, Anton Anderledy.

Though his historical interests began as a hobby, Devitt eventually became an editor of the Woodstock Letters, a journal published by the American Jesuits.

For his historical work, Devitt received the posthumous praise of Bishop Thomas Shahan, the rector of the Catholic University of America and a historian.