Graduate of the Faculty of Animal Science at the Bydgoszcz University of Technology.

In 1990, he started work as director of the Department of Agriculture at the Voivodship Office in Szczecin, and between 1992 and 1995 he became director of a branch of the Agricultural Property Agency in Szczecin. In 1993, he was appointed Secretary of State in the Ministry of Agriculture and Food Economy in Hanna Suchocka's government. In 1995-1997, he served as Director of Settlement at the Agricultural Property Agency. In 1997, he became Chairman of the Conservative People's Party (Stronnictwo Konserwatywno-Ludowe), Member of Parliament of the Republic of Poland and Minister of Agriculture and Rural Development in Jerzy Buzek's government.

In 2004 he defended Phd thesis at UKSW University in Warszawa entitled: Adaptation problems of the Polish countryside and agriculture in the context of integration with the European Union.

Since leaving politics, he has run a business and worked as an assistant professor at several universities, currently at the Higher School of Management in Konin. Jacek Janiszewski is also the founder and chairman of the programme board of the Integration and Cooperation Association. In 1994, he initiated one of the largest economic and business meetings in Poland, initially held in Międzyzdroje and Ciechocinek, and now in Toruń under the name Welconomy Forum in Toruń.

In 2011, Dr Jacek Janiszewski was awarded the Commanders Cross of Polonia Restituta.