Sickel did not see action again until the Spring of 1864 when he was ordered to join the forces of George Crook operating in western Virginia, where he commanded the 3rd Brigade of Crook's Kanawha Division. At the Battle of Cloyd's Mountain, he led his men in a charge against the Confederate breastworks which succeeded in turning the enemy's flank. The following month the three-year enlistments of the 3rd Pennsylvania Reserves ran out. Sickel and the rest of his men were mustered out of the volunteer services on June 17, 1864. He immediately reenlisted and was appointed colonel of the 198th Pennsylvania Infantry. This command was ordered to the Petersburg front and upon arrival there, Sickel was placed in command of the 1st Brigade in the 1st Division of the V Corps. Two weeks later Sickel led his brigade into action at Poplar Springs Church. For his services there he was given a brevet promotion to brigadier general of volunteers on October 21, 1864. Sickel took a supporting role in the Battle of Boydton Plank Road but was again significantly engaged at Hatcher's Run. There he received a painful flesh wound in his left thigh on February 6, 1865. This wound bothered him for the remainder of his life. In November 1864 General Joshua L. Chamberlain, permanent commander of the 1st Brigade, returned to duty and Sickel reverted to regimental command. He was given a brevet promotion to major general on March 13, 1865. At the Battle of Quaker Road, Sickel "greatly distinguished himself", according to Chamberlain, "...and [behaved] in the most admirable manner." He was again wounded at Quaker Road, having his horse shot out from under him. It was believed at the time that his arm would have to be amputated, his arm was saved but he lost his elbow. He mustered out of the volunteer service on June 4, 1865.