After briefly working as a primary school teacher Kersten was inducted into his first pastorate in Meliskerke in 1905 without formal theological training.

Eleven years later, in 1918, he established the Reformed Political Party to realize his vision of "a Calvinist Netherlands ruled on a biblical basis without cinema, sports, vaccination and social security".

On the evening of 10 November 1925, Kersten, ever opposed to Catholicism, proposed an amendment to the 1926 budget for the Ministry for Foreign Affairs.

The speaker of the Dutch parliament had parts of Kersten's contributions to debates edited in the Proceedings no less than thirteen times between 1922 and 1940.

[2] During World War II, Kersten denounced resistance against the Nazis, claiming the occupation of the Netherlands was a deserved divine punishment for desecration of the Lord's Day (Sunday).