Karl Schleinzer was born in 1924 in the Austrian Lavanttal valley.

After an apprenticeship as a farmer, he was elected to the Carinthian parliament in 1956. In 1959, he became provincial party chairman of the Austrian People's Party in Carinthia and for the next two years he held the office of provincial councillor for agriculture and forestry there.

From 1961 to 1964, he was Austria's Minister of Defense under Federal Chancellor Alfons Gorbach. Under his successor Josef Klaus, Dr. Schleinzer was Federal Minister of Agriculture and Forestry until 1970.

After the change of government in Vienna, he led the opposition with his conservative People's Party and was finally nominated as the top candidate for the 1975 National Council elections. On July 19 of the same year, he was killed in a car accident on his way back from an election campaign event.

During his time as Federal Minister of Agriculture and Forestry, he accepted an invitation to visit the Federal Republic of Germany and also visited Wiesbaden in February 1967. Together with Frank Seiboth, State Secretary in the Hessian Ministry of Agriculture, the statesman was received by Lord Mayor Buch in the ballroom of the town hall on February 23. After brief speeches focusing on German-Austrian ties and the town twinning of Wiesbaden and Klagenfurt, Dr. Karl Schleinzer signed the city's Golden Book.