On enlisting in the Navy, 17 March 1862, he was assigned to stern wheel gunboat Marmora. On 5 March 1864, during a Confederate assault on Union positions at Yazoo City, Mississippi, Laffey landed a 12-pound howitzer and her crew. In the face of enemy rifle fire, which cut up the gun carriage and severed the rammer, Laffey bravely stood by his gun and contributed greatly to turning back the attack. For this action, Seaman Laffey was awarded the Medal of Honor.
He died at Chelsea, Mass., 22 March 1901.