In the First Balkan War, fought from October 1912 to May 1913, Pećanac was mobilised in the Serbian Third Army, holding the rank of sergeant in the Morava Division. He took part in the defeat of the Albanians in Merdare, the Battle of Kumanovo and the capture of Metohija. During the Second Balkan War, fought from 29 June to 10 August 1913, Pećanac is believed to have been stationed at the front at Kitka on Osogovo Mountain along the Zletovska and Bregalnica rivers. There, his division took part in the Battle of Bregalnica with the Bulgarians. After the Bulgarian attacks failed, they sent parliamentarians to seek a truce, but the Serbian side refused and the fighting continued. After his division had endured six days of heavy fighting, the Bulgarians were defeated at Grljani near Vinica.