[1] Josias was born at Eisenberg Castle on 18 March 1554[2][3] as the sixth child of Count Wolrad II 'the Scholar' of Waldeck-Eisenberg and Countess Anastasia Günthera of Schwarzburg-Blankenburg.

[1] Already at the beginning of his reign, he succeeded in creating an important accent, whose unifying direction was, however, tempered by confessional differences.

To finance the state school the properties of Berich Abbey [de], which had previously been administered by the count's family, were sold.

[note 1] Because of the Protestant orientation, however, there were differences of opinion, as a result of which some of the renowned professors left the school in 1586 and moved to the Calvinist-oriented Academia Nassauensis in Herborn.

He died suddenly and unexpectedly on 6 August 1588[2][3][6] at Eisenberg Castle,[2][6] where guests from the baptism of his fourth child, Wolrad IV, were still staying.

[3] He was succeeded by his underage sons Christian and Wolrad IV, who were under the custody and regency of their mother and Count Francis III of Waldeck-Landau [de].