On July 25th, 1861 he was transfered to the 19th Mass. Volunteers and served with this regiment until the end of the war. Of the 37 original commissioned officers of the 19th Massachusetts, Edmund Rice was the only one to serve the entire war and came home in 1865 as colonel and commanding officer.

From July, 1861 until September, 1862, he was engaged in the following battles: Balls Bluff, Penninsula Campaign, Myron's Mills, Siege of Yorktown, West Point, Fair Oaks, Oak Grove, Peach Orchard, Allen's Farm, Savage Station, White Oak Swamp, Glendale, Malvern Hill, Second Malvern Hill, Bull Run, Fairfax Court House, South Mountain and Antietam.He commanded the regiment at Glendale and was mentioned in the general orders for his conspicuous bravery.

He was severely wounded by canister shot at the battle of Antietam,Sept. 15, 1862, and was on sick leave until October 1862, when he rejoined his regiment at Falmouth. He was commissioned major on October 1, 1862 and participated in the second attack on Fredericksburg and the action at Thoroughfare Gap.

At the battle of Gettysburg, he rendered conspicuous service, and was presented by Congress with the Medal of Honor, for leading the advance of the 19th Massachusetts and the 42nd New York, in the charge made to close the gap in our line, and repel Pickett's charge.

The Medal of Honor is engraved: "The Congress to Lieut.-Col. Edmund Rice, 19th Mass. Vols. for conspicuous bravery on the 3rd day of the battle of Gettysburg."

Documents on file in the War Department at Washington, of this incident say the following: "The conspicuous gallantry of Major Edmund Rice, of the 19th. Mass. Vols. Infantry, at the third day's battle of Gettysburg, where he was severely wounded, did more than the single exertion of any other officer on our side to retrieve the day after the battle had been virtually won by the confederates, who had broken our lines, and were cheering and swinging their
hats on our captured guns. After the line was broken, the 19th dashed in and placed themselves in the rear of the break, and for twelve minutes received the enemy's fire, at a distance of less than fifteen paces. In that time one man in every two of the whole regiment, and seven fell over, including Rice, who was shot in front of his men with his his foot on the body of a fallen confederate, he being at that moment the officer fighting nearest to the enemy in our whole line. He fought till he fell; his men fought till they fell. He held Pickett's heavy column in check with the single thin line of his regiment, till re-inforcements came from right and left..." "Rice's regiment lost three-fourths of its force in that awful struggle, but its victorious remnants brought off the field the captured battleflags of the 14th, 19th, 53rd and 57th Virginia Regiments. When Webb's brigade broke, the writer, recognizing fully the crisis of the moment, listened impatiently for the expected order to meet it, but except Rice's cry to follow him, heard no such order, and believes that none other was given."