Cohen a jurist by occupation, worked as a researcher for the Leiden University from 1971 until 1981 and for the State University of Limburg from 1981 until 1983. Cohen became a professor of jurisprudence at the State University of Limburg in 1983 and was appointed as rector of the State University of Limburg in 1991.
In 1993 Cohen was asked by the Labour Party to become Undersecretary for Education and Sciences in the Cabinet Lubbers III under Prime Minister Ruud Lubbers following the resignation of Roel in 't Veld. Cohen accepted and resigned as rector and professor the same day he took office as the new Undersecretary for Education and Sciences on 2 July 1993. After the Dutch general election of 1994 Cohen was asked to become Minister of Education and Science in the Cabinet Kok I under Prime Minister Wim Kok but refused after his wife was diagnosed with Multiple sclerosis.
Cohen remained Undersecretary for Education and Sciences until the Cabinet Kok I was installed on 22 August 1994. He returned to the State University of Limburg as rector and as a professor of jurisprudence in 1995. For the Dutch Senate election of 1995 Cohen was elected as a Member of the Senate taking office on 13 June 1995. On 1 August 1996 Cohen was selected as the Parliamentary leader of the Labour Party in the Senate. After the Dutch general election of 1998 Cohen was asked to become Undersecretary for Justice in the Cabinet Kok II. Cohen accepted and resigned as the Parliamentary leader of the Labour Party in the Senate and as a Member of the Senate and as rector and professor the same day the Cabinet Kok II was installed on 3 August 1998.
On 15 December 2000 Cohen was selected as Mayor of Amsterdam and resigned as Undersecretary for Justice on 1 January 2001 and took office as Mayor of Amsterdam on 15 January 2001.
On 12 March 2010 the Leader of the Labour Party Wouter Bos unexpectedly announced his retirement from national politics and stood down as Leader of the Labour Party, Cohen announced his resignation as Mayor of Amsterdam the same day and was elected as the Leader of the Labour Party on 25 April 2010 and became the Lijsttrekker (top candidate) for the Dutch general election of 2010. Following the election the Labour Party became the second largest party in the House of Representatives and Cohen was elected as the Parliamentary leader of the Labour Party in the House of Representatives and a Member of the House of Representatives on 17 June 2010. Cohen served as opposition leader against Prime Minister Mark Rutte and the Cabinet Rutte I.
On 20 February 2012 after increasing criticism on his performance as opposition leader Cohen announced his retirement from national politics and stood down as Leader of the Labour Party and Parliamentary leader of the Labour Party in the House of Representatives that same day. Cohen remained a Member of the House of Representatives until 29 February 2012.
Cohen semi-retired from active politics at the age of sixty-five and served as Chairman of the investigation committee for the Project X Haren-riots. Following the end of his active political career, Cohen occupied numerous seats on supervisory boards in several international non-governmental organizations (Ronald McDonald House Charities, Openbare Bibliotheek Amsterdam). Cohen has been the Chairman of the Social Affairs and Employment Trade association (Cedris) since 2013 and currently serves as professor of jurisprudence, public administration and political science at the Leiden University since 2014.
Marius Job Cohen was born in Haarlem in the province of North Holland. He is the second child (of two) of Adolf Emile "Dolf" Cohen (1913–2004) and Henriëtte "Hetty" Koster (1913–1996). His elder brother is Floris Cohen (born 1946).
His parents both studied history and became high school teachers of history. They were liberal (non-religious) Jews, and were forced into hiding until the end of World War II. His paternal grandparents Hendrik Cohen and Flora Polak both died in Bergen-Belsen concentration camp in 1945. After the war, his father worked at the Dutch Institute for War Documentation. Later he became a professor of medieval history and a rector magnificus at Leiden University. His mother became a member of the city council of Heemstede. His parents were both early members of the Labour Party.
Cohen went to a public primary school in Heemstede. He attended the secondary school Stedelijk Gymnasium in Haarlem from 1960 to 1966. He studied Dutch public law at the University of Groningen from 1966 and obtained his Master of Laws degree in 1971. During his student years, he was a member of the student association Vindicat atque Polit.
Cohen married Lidie Lodeweges on 2 July 1972 in Groningen. She studied Dutch language in Groningen and was a high school teacher. She had multiple sclerosis and needed a wheelchair. Cohen and his wife had two children, son Jaap (born 1980) and daughter Lotje (born 1983). Lidie Cohen died on 4 August 2015.
Between 1 September 1971 and 1 September 1981, Job Cohen held a scientific position at the Bureau Research of Education at Leiden University. He obtained a doctorate (PhD) from this university in June 1981, with a dissertation on the rights of university students.
On 1 September 1981 he joined the State University of Limburg in a higher scientific capacity, and was chairman of the commission that prepared the establishment of a faculty of law. On 1 September 1983 Cohen became professor of methods and techniques at the faculty of law; on 1 January 1991 he also became rector magnificus of the State University of Limburg. He resigned from this position to become State Secretary for Education and Sciences in 1993.
In 1995 he returned to his position in Maastricht as professor and rector magnificus at Maastricht University (the former State University of Limburg). From 1 January 1998, he took a sabbatical year, but he resigned in August 1998 when he became State Secretary for Justice.
Cohen has received two honorary degrees for his contributions to law and society, one in 2007 from the University of Windsor and one in 2008 from the Radboud University Nijmegen.
On 2 July 1993, Cohen became State Secretary (deputy minister) for Education and Sciences in the third cabinet of Ruud Lubbers, under education minister Jo Ritzen. In Cohen's portfolio were higher and academic education, science policy, and adult education. The term of this post expired after a year and Cohen returned to his academic post in Maastricht.
From 13 June 1995, Cohen was a member of the Senate of the Netherlands. Between 1 August 1996 until he resigned from the Senate on 3 August 1998, he was also the parliamentary group leader of the Labour Party in the Senate.
During his period in the Senate, he also worked for the Maastricht University, where he began a sabbatical year on 1 January 1998. In February 1998 however, he took on the function of interim-director of the broadcasting organization VPRO, lasting until 15 August.
On 3 August 1998, he resigned from the Senate to take up the position of State Secretary for Justice in the second cabinet of Wim Kok, dealing chiefly with immigration. In this capacity he was responsible for a new immigration law, intended to restrict entry of refugees to "genuine cases".
He resigned his position as State Secretary on 31 December 2000 in order to take up the position of Mayor of Amsterdam (burgemeester) on 15 January 2001. Mayors of Dutch cities are appointed by the cabinet in the name of the monarch.
At midnight on 1 April 2001, Cohen became the first public official to wed same-sex couples, following the passing of legislation opening up marriage to people of the same gender (see Same-sex marriage in the Netherlands).
On 2 February 2002, Job Cohen performed the civil marriage of Prince Willem-Alexander and Máxima Zorreguieta in the Beurs van Berlage in Amsterdam.
In November 2004, controversial film maker Theo van Gogh was killed in Amsterdam by a Muslim extremist. Time awarded Cohen the title "European Hero" in 2005, for his inclusive approach towards the Muslim community after the murder, defusing tension in the city.
Cohen found himself thrown into the role of mediator between the city's Muslims, the original Dutch population and other groups in the cultural and racial mix. Almost half Amsterdam's residents are of non-Western descent, a majority of them Muslims."Islam is here to stay, in this country, in this city (...) We have to deal with Islam as a fact, not whether we like it. So the real question is how to get on with each other." Cohen took pride in the fact that in Amsterdam no violence or arson occurred in response to the killing. By his visiting ethnic groups, organizing debates among religious leaders and his listening and promoting dialogue, he received from opponents the mocking nickname of "tea drinker" – an image that would be exploited by them when he returned in the Dutch national politics in 2010.
On 27 January 2006 Cohen announced he would be willing to serve a second term as mayor of Amsterdam. On 12 July 2006 the municipality of Amsterdam almost unanimously (Democrats 66 opposed, being in favour of an elected mayor) supported Cohen to prolong his career as a mayor after 15 January 2007 when his first term ended. The Queen's Commissioner Harry Borghouts of North Holland will now have to offer this advice to the Ministry of Internal Affairs.
Cohen's politics towards ethnic minorities in Amsterdam is characterized by the slogan "keeping things together" (de boel bij elkaar houden). On 2 May 2006 Immigration Minister Rita Verdonk of the centre-right VVD accused Amsterdam of becoming a "banana republic", with a lax safety policy: she cited the criminal liquidations and the disturbance caused by young people as examples of this. In the yearly crime meter of the Algemeen Dagblad Amsterdam did not perform particularly badly in safety policy and crime fighting, one of the reasons for this is Cohen's targeted approach towards those who commit multiple crimes (veelplegers). Cohen stated that his policy which combines soft and hard approaches, fighting crime and fighting the causes of crime, was the key to his successful safety policy.
In 2006 the World Mayor organization determined Cohen to be runner-up in the award for World Mayor of 2006, behind Melbourne mayor John So, and ahead of Harrisburg mayor Stephen R. Reed. World Mayor praised Cohen's leadership following the murder of Theo van Gogh in 2004, and his efforts at bringing together the diverse population of Amsterdam.
In late 2007, Cohen moved to reduce prostitution in Amsterdam, following allegations that Hells Angels and other organized criminals had taken over the prostitution industry. The city council bought 18 buildings in the red light district De Wallen from Charlie Geerts in order to convert them into upscale establishments and revoked the license of the luxury brothel Yab Yum.
On 12 March 2010, Wouter Bos resigned as leader of the Labour Party. Bos named Cohen as candidate for the position, which he accepted. At the subsequent elections, Cohen was a candidate for Prime Minister. He was expected to be a strong opponent to Geert Wilders and was described in the press as "authoritarian but enlightened." Exit polls showed the Labour Party as the second largest with 30 seats and 19.6% of the total vote. Eventually his opponent Mark Rutte of the VVD became the Prime Minister of the Netherlands.
He has been chair of the Labour Party in the House of Representatives since 10 June 2010 and a member of the House of Representatives since 17 June 2010.
On 20 February 2012, he resigned as leader of the Labour Party, he also left the House of Representatives over criticisms that he had been too moderate towards the center-right Dutch government's planned economic austerity measures and the Dutch government's support for the EU Commission's plan to bail out Greece, which had been passed with the support of the Dutch Labour Party. At the time of his resignation, the Dutch Socialist Party, which was to the left of the Dutch Labour Party, had overtaken the Dutch Labour Party in a number of opinion polls.Knight in the Order of the Netherlands Lion (1994), queen of the Netherlands
Knight in the Order of Orange-Nassau (2003), queen of the Netherlands
European Hero (2005), Time Magazine
Best Mayor of the Last 25 Years (2005), Binnenlands Bestuur
Citizenship Award (2005), P&V Foundation
Honorary degree (2007), University of Windsor, Ontario, Canada
Advertising Man of the Year (2007), Marketing Tribune
Honorary degree (2008), Radboud University Nijmegen
Martin Luther King Award (2008), DutchVersity
Cross of Recognition, Second Class (2008), president of Latvia
Gold Medal (2010), city council of Amsterdam
Books (as author)
Studierechten in het wetenschappelijk onderwijs (1981), dissertation
Wandeling door een historisch besluit (2003)
Binden (2009), collection of speeches and lectures
Audio books (as narrator)
Het grijze kind (2007), novel written by Theo Thijssen
De Uitvreter (2008), novella written by Nescio
Lijmen/Het Been (2009), two novellas written by Willem Elsschot
Kaas (2009), novella written by Willem Elsschot
Titaantjes (2010), novella written by Nescio
Max Havelaar (2010), novel written by Multatuli
Reizen zonder John (2012), non-fiction written by Geert Mak
Het dwaallicht (2013), novella written by Willem Elsschot
De eeuw van mijn vader (2013), non-fiction written by Geert Mak
De levens van Jan Six (2016), non-fiction written by Geert Mak