In Finland, he belonged to the club Kotkan Riento. At the Summer Olympics in Stockholm in 1912 he was at featherweight before Georg Gerstacker from Nuremberg and Otto Lasanen from Finland Olympic champion. On the way to the gold medal he had shouldered five of his eight opponents, including Gerstacker. In the Finnish Civil War in 1918 he fought as a Red Guard in Savitaipale in South Karelia. After the war and the defeat of the Red Guards, he fled to Russia, from where he emigrated to the United States. There he founded a sauna companies. The 1.72 meter tall Kaarlo Koskelo was considered a great talent and hope the Finnish ring sport, however, remained his Olympic appearance in 1912 in Stockholm, his only major tournament. In Finnish Championships he had never gone to the start.