In 1339, he succeeded his older brother Fritzli II as Count of Hohenzollern.
On 27 July 1342, he closed a treaty of agnatic seniority with the Zollern-Schalksburg line, in which the senior of the two counts should decide who would be the next holder of the original fief of Zollern.
As Friedrich commanded a larger military power, he became a captain of the Lion League, an important organisation of Swabian noblemen.
[1] In 1412, the Strasbourg line founded by his brother inherited the county; they were later raised to Princes of Hohenzollern.
In 1341 Fredrick IX married Adelheid (d. after 1385), a daughter of Count Burchard V of Hohenberg-Wildenberg, with whom he had the following children: