Since he was too young to take over at this age, the country was ruled by a regency council consisting of Landgrave Philip I of Hesse, Count Adolph of Schaumburg and Count Jobst II of Hoya.

This met with the disapproval of the Emperor Charles V, whose troops occupied Lippe in the course of the Schmalkaldic War (1546–1547) and, after the defeat of the Protestant side in 1548, began implementing the Augsburg Interim.

In 1555, Bernard visited the Diet of Augsburg in person, and in 1556, he convened a meeting of the Protestant clergy in his county.

In 1559, Bernhard gave Sternberg Castle to his brother Herman Simon as a Paréage.

His marriage to Catherine (1524–1583), daughter of the Count Philip III of Waldeck-Eisenberg produced the following children: