Abdullah is said to have been born on 1 August 1924 in Riyadh. However, some sources state that this date is incorrect, and that he was approximately eight years older. He was the tenth son of King Abdulaziz. His mother, Fahda bint Asi Al Shuraim, was a member of the Al Rashid dynasty, longtime rivals of the Al Saud dynasty. She was descended from the powerful Shammar tribe – and was the daughter of former tribe chief, Asi Shuraim. She died when Abdullah was six years old. He had younger full-sisters.

Abdullah, like Fahd, was one of the many sons of Ibn Saud, the founder of modern Saudi Arabia. Abdullah held important political posts throughout most of his adult life. In 1961 he became mayor of Mecca, his first public office. The following year, he was appointed commander of the Saudi Arabian National Guard, a post he was still holding when he became king. He also served as deputy defense minister and was named crown Prince when Fahd took the throne in 1982. After King Fahd suffered a serious stroke in 1995, Abdullah became the de facto ruler of Saudi Arabia until ascending the throne a decade later.

King Abdullah was Commander of the Saudi National Guard from 1963 to 2010. He was Chairman of the Saudi Supreme Economic Council until 2009. He also continued to be the President of the High Council for Petroleum and Minerals, President of the King Abdulaziz Center For National Dialogue, Chairman of the Council of Civil Service, and head of the Military Service Council until his death in 2015.

King Khalid appointed Prince Abdullah as second deputy prime minister in March 1975, a reflection of his status as second in the line of succession to the Saudi throne. In other words, upon this appointment, Prince Abdullah became the number three man in the Saudi administration. However, his appointment caused friction in the House of Saud. Then-crown Prince Prince Fahd, together with his full-brothers known as the Sudairi Seven, supported the appointment of their own full brother, Prince Sultan. Prince Abdullah was pressured to cede control of SANG in return for his appointment as Second Deputy Prime Minister. In August 1977, this generated a debate among hundreds of princes in Riyadh. Abdullah did not relinquish authority of SANG because he feared that this would weaken his authority.

King Abdullah had long been pro-American and a longtime close ally of the United States. In October 1976, as Prince Abdullah was being trained for greater responsibility in Riyadh, he was sent to the United States to meet with President Gerald Ford. He again traveled to the United States as Crown Prince in October 1987, meeting Vice President George H. W. Bush. In September 1998, Crown Prince Abdullah made a state visit to the United States to meet in Washington with President Bill Clinton. In September 2000, he attended millennium celebrations at the United Nations in New York City. In April 2002, Crown Prince Abdullah made a state visit to the United States with President George W. Bush and he returned again in April 2005 with Bush. In April 2009, at a summit for world Leaders President Barack Obama met with King Abdullah, while in June 2009 he hosted President Obama in Saudi Arabia. In turn, Obama hosted the King at the White House in the same month.

On 13 June 1982 – the day King Khalid died – Fahd bin Abdulaziz became King, Prince Abdullah became Crown Prince the same day and also maintained his position as head of the National Guard. During his years as crown Prince, Abdullah bin Abdulaziz was described as a supporter of accommodation. He managed to group a large number of fringe and marginalized princes discontented with the prospect of the succession being passed among the Sudairi brothers one after the other. His control of the National Guard was also a key factor to his success in becoming crown Prince. When King Fahd was incapacitated by a major stroke in 1995, Crown Prince Abdullah acted as de facto regent of Saudi Arabia.

King Abdullah's eldest son, Prince Khaled, was deputy commander of the Saudi Arabian National Guard West until 1992. His second son, Prince Mutaib, is former commander and current minister of the National Guard. His mother is Munira Al Otaishan. Prince Mishaal was governor of the Makkah Province (2013–2015). Prince Abdulaziz was the king's former Syria adviser and has been deputy foreign affairs minister since 2011. Prince Faisal is head of the Saudi Arabian Red Crescent Society. King Abdullah's seventh son, Prince Turki, who was a pilot in the Royal Saudi Air Force, was governor of the Riyadh Province (2014–2015). The youngest son, Prince Badr, was born in 2003, when Abdullah was about 79 years old. In October 2015, his son, Prince Majed bin Abdullah bin Abdulaziz Al Saud, was arrested in Los Angeles for using cocaine, being drunk, threatening female employees, and having gay sex with a male employee.

In August 2001, he ordered then Saudi Ambassador to the US, Bandar bin Sultan, to return to Washington. This reportedly occurred after Crown Prince Abdullah witnessed brutality inflicted by an Israeli soldier upon a Palestinian woman. Later, he also condemned Israel for attacking families of suspects.

In 2002, he developed the Arab Peace Initiative, commonly referred to as the "Abdullah plan", to achieve a mutually agreed-on resolution of the Arab–Israeli conflict. The initiative was adopted at the Arab League's Beirut summit in March 2002.

On 16 February 2003, Parade magazine's David Wallechinsky rated King Fahd and Crown Prince Abdullah as the second worst dictators in the world. Most of this criticism stems from the fact that most of Saudi citizens live under a strict Wahhabist interpretation of Sharia law, which mandates the amputation of hands as a punishment for theft and floggings for crimes like drunkenness. Execution by public beheading is Common for murder, rape, drug trafficking and witchcraft, and Abdullah's policies towards the rights of women have also been criticized. In a slight rebuff to accusations of human rights violations, Saudi inmates of Najran Province sent the King well-wishes from jail and wished him a speedy recovery.

In 2005, King Abdullah implemented a government scholarship program to send young Saudi men and women abroad for undergraduate and postgraduate studies in different universities around the world. The program offered funds for tuition and living expenses up to four years. It is estimated that more than 70,000 young Saudis studied abroad in more than 25 countries, with the United States, England, and Australia as top three destinations aimed for by the students. There are more than 22,000 Saudi students studying in the United States, exceeding pre-9/11 levels. Public health engagement included breast cancer awareness and CDC cooperation to set up an advanced epidemic screening network to protect 2010's three million Hajj pilgrims.

Since King Abdullah's visit to Beijing in January 2006, Saudi-Chinese relations have focused predominantly on Energy and trade. The king's visit was the first by a Saudi head of state to China since the two countries established diplomatic ties in 1990. Bilateral trade with China has more than tripled, and China would soon be Saudi Arabia's largest importer. Saudi Arabia also committed significant Investments in China, including the $8 billion Fujian refinery. Based on a WikiLeaks cable, the King told the Chinese that it was willing to effectively trade a guaranteed oil supply in return for Chinese pressure on Iran not to develop nuclear weapons.

On 30 October 2007, during a state visit to the UK, King Abdullah was accused by protestors of being a "murderer" and a "torturer". Concerns were raised about the treatment of women and homosexuals by the Saudi kingdom and over alleged bribes involving arms deals between Saudi Arabia and the UK.

In April 2008, according to a US cable released by Wikileaks, King Abdullah had told the US Ambassador to Iraq, Ryan Crocker, and General David Petraeus to "cut off the head of the snake". Saudi Arabia's Ambassador to Washington, Adel al-Jubeir, "recalled the King's frequent exhortations to the US to attack Iran" and to put an end to that country's nuclear program. King Abdullah asserted that Iran was trying to set up Hezbollah-like organizations in African countries, observing that the Iranians didn't think they were doing anything wrong and didn't recognize their mistakes. He said that the Iranians "launch missiles with the hope of putting fear in people and the world". The King described his conversation with Iranian foreign minister Mottaki as "a heated exchange, frankly discussing Iran's interference in Arab affairs". When challenged by the King on Iranian meddling in Hamas affairs, Mottaki apparently protested that "these are Muslims". "No, Arabs", countered the King. "You as Persians have no Business meddling in Arab matters". King Abdullah said he would favor Rafsanjani in an Iranian election.

King Abdullah supported renewed diplomatic relations with the Syrian government and Bashar al-Assad. They met in Damascus on 7 October 2009. In addition, Assad attended the opening of King Abdullah University of Science and Technology in October 2009. Relations between Syria and Saudi Arabia deteriorated as a result of the Syrian Civil War. In August 2011, King Abdullah recalled the Saudi Ambassador from Damascus due to the political unrest in Syria and closed its embassy.

In November 2010, his back problems came to light in the media. He had an "accumulation of blood" around the spinal cord. He suffered from a herniated disc and was told to rest by doctors. To maintain the Kingdom's stability, Crown Prince Sultan returned from Morocco during the King's absence. The King was admitted to New York-Presbyterian Hospital after a blood clot complicated a slipped disc and underwent successful back surgery. The lead surgeon was Muhammad Zaka, who probably removed the herniated disk and performed a lumbar fusion. He subsequently had another successful surgery in which Surgeons "stabilized a number of vertebras". He left the hospital on 22 December 2010 and convalesced at The Plaza in New York City. On 22 January 2011, he left the United States and for Morocco, and returned to the Kingdom on 23 February 2011.

In 2011, the financial magazine Forbes estimated his and his immediate family's documentable wealth at US$21 billion, making him one of the world's richest monarchs.

In April 2012, he was awarded by the United Nations a gold medal for his contributions to intercultural understanding and peace initiatives.

From his marriage to Princess Alanoud Al Fayez (arranged when she was 15 without her having ever met him), whom he has now divorced, he had four daughters – Princesses Sahar, Maha, Hala and Jawahir. The four princesses have been under house arrest for the last 16 years, and are not allowed to leave the country. After media releases in March 2014, Sahar and Jawaher received no food or clean water for 25 days, lost 10 kilos each and their mother carried out weekly protests in front of the Saudi Arabian embassy in London, and about which Sahar and Jawaher released a video while under house arrest pleading for help from the international community. King Abdullah also had a daughter called Princess Nora who died in 1990 in a car accident. Princess Fayza is yet another daughter. She is the mother of Prince Saud bin Abdulaziz bin Nasser Al Saud who was accused of murdering his servant Bandar Abdulaziz in London in 2010.

He told General Jones that Iranian internal turmoil presented an opportunity to weaken the regime—which he encouraged—but he also urged that this be done covertly, stressing that public statements in support of the reformers were counterproductive. The King assessed that sanctions could help weaken the government, but only if they are strong and sustained.

The King outlived two of his crown princes. Conservative Interior Minister Nayef bin Abdul-Aziz Al Saud was named heir to the throne on the death of Sultan bin Abdulaziz in October 2011, but Nayef himself died in June 2012. Abdullah then named 76-year-old defense minister, Salman bin Abdulaziz Al Saud, as crown Prince. According to various reports, Abdullah married up to 30 times and had more than 35 children. The king had a personal fortune estimated at US$18 billion, making him the third wealthiest head of state in the world. He died on 23 January 2015, at the age of 90, three weeks after being hospitalized for pneumonia, and was succeeded as king by his half-brother Salman of Saudi Arabia.