After military service in Europe during World War I and subsequent convalescence, Holland became important in business and politics in Christchurch, N.Z. In 1935 he replaced his father, Henry H. Holland, in Parliament and became leader of the National Party opposition in 1940. Holland served briefly (1942) in the war Cabinet but thereafter attacked the Labour-led government for its economic controls and mismanagement. Under him, the National Party won office in 1949. Holding the finance portfolio in the first five years of his ministry, Holland reduced controls on imports, prices, and property transactions, and increased food subsidies. Balance of payments crises (1952, 1954) and continued inflation, however, led him to reinstitute many of the economic controls that had been imposed by Labour in 1940–49.

In 1950 Holland converted New Zealand's government to a one-chamber system by gaining abolition of the Legislative Council, the country's upper house. The following year, he capitalized on his success in repressing a dockmen's strike by immediately calling an emergency election in which he increased his parliamentary majority, but his subsequent bill (1951) to increase police powers in industrial conflicts (at a loss, many felt, of important individual rights) was enacted only in an amended form after a public outcry. Discontent with economic conditions caused the party's defeat in 1957. Holland retired before the 1957 elections because of poor health. In that year he was knighted.