Historically, Burg Altenfils was first mentioned around 1180 in the property register of Count Siegfried von Bonenburg, who died in 1144. It then passed by inheritance to the Duke of Saxony, Henry the Lion, and is mentioned again in 1200 in the division agreements of his sons. The Altenfels is not mentioned again until the end of the century, in 1294. The Archbishop of Cologne promised the citizens of Brilon, who had helped rebuild his castle, that they would not be harmed by it in the event of war. In 1307, 1325 and 1326, castle men are still mentioned at the castle, so it can be assumed that it still existed at this time.