After the 1959 general election Marijnen was appointed as Minister of Agriculture and Fisheries in the De Quay cabinet, taking office on 19 May 1959.

Marijnen also became active in the public sector as a non-profit director and served on several state commissions and councils on behalf of the government.

During his premiership, his cabinet was responsible for several major reforms to health insurance, the public broadcasting system and dealing with the fallout of the marriage between Princess Irene and carlist Carlos Hugo of Bourbon-Parma.

In 1941 he graduated in law from the Radboud University Nijmegen and went on to work in the accountancy divisions of the Ministry of Agriculture, Nature and Food Quality.

"[5] The Dutch Catholic Church organised the castration of Heithuis while he lived at the Gelderland children's home in 1956 after he reported being sexually abused to the police.

Despite this being the second cabinet without socialist Labour Party, the building up of a welfare state, that was started after World War II, continued with the introduction of minimum wages in 1964 and the national health service.