He came from the German-Baltic noble family Pilar von Pilchau, who were in the service of the Swedish and Russian crowns.
His parents were Fredrik Adolf Woldemar Baron Pilar of Pilchau, Lord of Audern (1814–1870) and Berta Johann Caroline von Ungern-Sternberg from the House of Grossenhof (1826–1903).
In 1899 he was elected the land councillor of Livonia which was a high position in the local government of Baltic Germans.
From 1908 to 1918 von Pilchau served as the land marshal [Wikidata] of Livonia, the leader of the noble corporation.
He was one of the persons behind the creation of the short-lived United Baltic Duchy and the only Chairman of its Regency Council from 5 to 28 November 1918.