Cabinet positions held during his political career include Minister of Industry and Tourism; Minister of Foreign Affairs and Foreign Trade; Minister of Development, Planning and Production; Minister of Finance and Planning.
Patterson received his secondary education at one of Jamaica's most prominent learning institutions, Calabar High School, before moving on to pursue higher studies at the University of the West Indies Mona Campus, and later the London School of Economics.
While pursuing his bachelor's degree at the University of the West Indies, he served as Chairman of the university’s External Affairs Commission, where he gained exposure to world leaders and international political thought through attendance at a number of international student fora. It was also at university that he developed a commitment to Caribbean regionalism as well as to the causes of the countries of the developing world.
His time as a Law student of the London School of Economics consolidated the foundation in international politics than his university experience in Jamaica had provided.
During his enrolment at the Inns of Court (Middle Temple) he again came in contact with a number of future leaders of the countries of the developing world who were fellow students in England.
Patterson entered the Parliament of Jamaica as an Opposition Senator in 1969, appointed by Opposition Leader Norman Manley. He was elected the youngest ever Vice President of the People's National Party later that year at age 33.
When in 1969 his predecessor as Prime Minister of Jamaica, Michael Manley, launched his campaign for the Presidency of the PNP, he turned to P. J. Patterson, youngest of the highest-ranking segment of the party executive, to lead his campaign. This was the beginning of a partnership which endured over the next 23 years, and allowed for an exchange of political ideas and perspectives that proved beneficial to both.
Patterson was elected the Member of Parliament for Westmoreland South Eastern in the constituency's by-election of 1970. The constituency borders were reorganized prior to the general election of 1993 and he was elected as the Member of Parliament for Westmoreland Eastern in that election, a seat he held until his retirement in 2006.
He was Campaign Manager for the People's National Party's bid for power in the General Elections of 1972, demonstrating skill as a political organizer that played a significant role in the party’s victory at the polls that year. This led to his first appointment to the Jamaican Cabinet. As his political career advanced, Patterson held diverse portfolio responsibilities in the Jamaican government for areas as varied as trade and industry, tourism, foreign affairs, finance and planning.
He assumed office as Prime Minister after Michael Manley retired in 1992, at a time when the Caribbean island nation was facing the formidable challenge of securing a place in a new global order of economic liberalization and deregulation.
Patterson led efforts to strengthen the country’s social protection and security systems—a critical element of his economic and social policy agenda to mitigate, reduce poverty and social deprivation.
His massive investments in modernization of Jamaica’s infrastructure and restructuring of the country's financial sector are widely credited with having led to Jamaica’s greatest period of investment in tourism, mining, ICT and energy since the 1960s. He also ended Jamaica’s 18-year borrowing relationship with the International Monetary Fund, allowing the country greater latitude in pursuit of its economic policies.
In September 2003 Patterson told a party conference that he wanted Jamaica to be a republic by the time he left office in 2007, saying "The majority of people in Jamaica are ready to consign to history the last vestiges of colonialism". Patterson had long supported moves to make Jamaica a republic, but he was unsuccessful in this aim, as when he left office Jamaica was still a monarchy. In 2012 he expressed his frustration that a republic had still not come into being
He made international headlines in 2004 when, as Chairman of CARICOM, he led the regional organization in the decision to refuse recognition of the Gérard Latortue government in Haiti following the removal of the democratically elected Jean-Bertrand Aristide from office. Patterson arranged for Aristide to take up temporary residence in Jamaica during Aristide's lawsuit against the United States and France accusing the countries of kidnapping him.
In one of his final initiatives as Prime Minister, he launched a program of radical transformation of the island’s education system aimed at development of quality human capital equipped to succeed in the competitive global economy. In addition, Patterson presided over a significant decline in poverty during his time in office.
Following his premiership, from 2006 to 2007, he chaired the Committee on Commonwealth Membership, which presented its report on potential changes in membership criteria for the Commonwealth of Nations at the Commonwealth Heads of Government Meeting 2007 in Kampala, Uganda.
Patterson is a member of the Club de Madrid, a group that consists of more than 100 former Presidents and Prime Ministers of democratic countries, which works to strengthen democracy and democratic leadership worldwide.
Patterson has contributed to numerous Conventions and Statements in the international arena including the Valletta Statement on Multilateral Trade and the Gozo Statement on Vulnerable Small States. These have helped to shape north-south relationship and influence the negotiating position of developing countries.
He is a member of the Global Leadership Foundation, an NGO composed of a number of former statesmen, ex-presidents and Prime Ministers founded in 2004 by former State President of South Africa and Nobel Prize laureate F. W. de Klerk. The Global Leadership Foundation is an organization which works to support democratic leadership, prevent and resolve conflict through mediation and promote good governance in the form of democratic institutions, open markets, human rights and the rule of law. It does so by making available, discreetly and in confidence, the experience of former leaders to today’s national leaders. It is a not-for-profit organization composed of former heads of government, senior governmental and international organization officials who work closely with Heads of Government on governance-related issues of concern to them.
He played a seminal role in the process that marked the transition from the first steps in integration of the Caribbean region to the founding of CARIFTA and its evolution into CARICOM. He drew upon his expertise in law and trade, to steer the regional body toward the development of a Caribbean jurisprudence through the Caribbean Court of Justice, and a borderless regional economy through the CARICOM Single Market, which came to fruition in 2005 and 2006 respectively.
During his tenure as Jamaica’s Foreign Minister he served as President of the ACP/EU Ministerial Council and led negotiations for the ACP group of countries with the European Community. As Chairman of the ACP/EEC Ministerial Conference, he played a pivotal role in forging an agreement on the basic framework for the original Lomé Convention, which influenced the outcome of subsequent negotiations that led to the Convention signed in 1975. He has served as President and Spokesman of the ACP Ministerial Council on a number of occasions.
A passionate opponent of apartheid, he was an ardent proponent of South Africa's liberation movement.
Upon becoming the Prime Minister of Jamaica in 1992 Patterson was invested with the Order of the Nation, allowing him to be known as "The Most Honourable" and to use the post-nominal letters "ON".
In 2006 he was invested with the Order of Excellence of Guyana,  allowing him to use the post-nominal letters "OE".