Eagen earned an undergraduate degree in 1927 at St. Thomas College in Scranton, Pennsylvania, before enrolling at Harvard Law School.

Eagen began clerking and studying law for Attorney James Powell, for which he received the sum of fifty dollars per month.

On February 25, 1977, Eagen became Chief Justice of the Pennsylvania Supreme Court serving in this role until his retirement from the bench in 1980.

On November 12, 1987, Eagen's portrait was hung in the Courtroom of the Pennsylvania Supreme Court in Philadelphia City Hall.

"[2] On May 4, 2018, the Main Courtroom in the Lackawanna County Courthouse, Scranton, Pennsylvania, was dedicated in honor of Chief Justice Michael J. Eagen.