Ernst of Schaumburg was the first Count of Schauenburg and Holstein-Pinneberg to earn the title of Prince in 1619. However, he died in 1622 without an heir. Schauenburg-Pinneberg had been a Lutheran region since his father Otto IV of Schaumburg had been won over to Martin Luther's teachings. After Ernst's death, a Catholic Count, Jobst Hermann, received a portion of Schauenburg but he also died without children, and Otto V, who was a Calvinist, succeeded Ernst.
Prince Ernst built the Stadthagen Mausoleum for himself and his family. Today, this building is estimated as a cultural monument of European rank.
On 11 September 1597 he married Hedwig of Hesse-Kassel at Wilhelmsburg Castle in Schmalkalden. The marriage remained childless.