McCarren received his country's highest award for bravery during combat, the Medal of Honor, for actions taken on July 3, 1863 during the Battle of Gettysburg.

At the onset of the Civil War, McCarren enlisted in Company H of the Irish-American three-months regiment, the 24th Pennsylvania under Thomas Alfred Smyth.

On the third day of this battle, McCarren captured the colors of the 13th Alabama in a counterattack against Pickett's Charge.

[1] The President of the United States of America, in the name of Congress, takes pleasure in presenting the Medal of Honor to Private Bernard McCarren, United States Army, for extraordinary heroism on 3 July 1863, while serving with Company C, 1st Delaware Infantry, in action at Gettysburg, Pennsylvania, for capture of flag.

[1] A division of the Ancient Order of Hibernians located in Newark, Delaware is named after McCarren.