Kempt was appointed to lead the 8th British Brigade in the army Wellington assembled in Belgium to invade France. The 8th Brigade consisted of the 1/28th, 1/32nd, 2/79th Highland and 1/95th Rifles in Sir Thomas Picton's 5th Division. At the Battle of Quatre Bras, Kempt's brigade was involved in heavy fighting and suffered 638 killed and wounded. At the Battle of Waterloo on 18 June, his brigade was again in the thick of combat and lost 681 killed and wounded. On Picton's death, Kempt succeeded to the command of the division. Early in 1815 he was made a Knight Commander of the Order of the Bath, and in July for his services at Waterloo, a Knight Grand Cross of the Order of the Bath.