Philip III and his nephew Count Philip IV of Waldeck-Wildungen appointed the Lutheran reformer Johann Hefentreger as pastor of the town of Waldeck.

On 26 June 1526, he led a Lutheran church service, thereby officially introducing the Reformation in the county, four months before Landgrave Philip I introduced the Reformation in neighbouring Hesse.

In 1529, the first Lutheran sermon was given in the St. Kilian Church in Korbach; he is portrait on the altar as its donor.

Between 1526 and 1530, Philip acquired the secularized former Aroldessen monastery of the Hospital Brothers of St. Anthony in Bad Arolsen and had it rebuilt to a Royal Palace.

In 1503, Philip married his first wife, Adelheid (d. 1515), a daughter of Count Otto IV of Hoya.