Mariusz Błaszczak was born on 19 September 1969 in Legionowo. He is a history graduate of the Faculty of History at the University of Warsaw. He is also a graduate of the National School of Public Administration and post-graduate studies in Local Government and Local Development and in Management in Administration.
After the studies, he worked in the local administration in the Legionowo City Hall. In the years 2002-2004, he was a deputy mayor of the Warsaw Wola district, and in December 2004 he became the mayor of the Śródmieście district.
From 31 October 2005, he was the Head of the Chancellery of the Prime Minister. In March 2007, the President of the Republic of Poland Lech Kaczyński appointed him as the Minister – a member of the Council of Ministers. He was elected in the 2007 parliamentary elections. He was re-elected in the 2011 elections. In 2015, he once again was elected a Sejm Deputy.
From 16 November 2015 he was the Minister of the Interior and Administration.
On 9 January 2018, he was appointed by the President of the Republic of Poland Andrzej Duda to the position of the Minister of National Defence.