Botha was born on the farm Telegraaf in the Paul Roux district of the Orange Free State , the son of Afrikaner parents. He was the only son of Pieter Willem senior (a widower with four children) and Hendrina Prinsloo/de Wet (a widow with five children). His father, also named Pieter, fought as a commando against the British in the Second Boer War (1899–1902). During the war his mother was interned in a British concentration camp . Botha's early education was at Paul Roux. Later he attended secondary school in Bethlehem before entering the University of the Orange Free State in Bloemfontein to study law. It was here that his political career began. Initially he helped organize the National Party (NP) during by-election campaigns and also became campus branch chairman.
Botha was also a part-time reporter for Die Volksblad and a member of the Afrikaanse Nasionale Studentebond (National Afrikaans Student Association). At the age of twenty he delivered an address to Prime Minister Malan on his visit to the campus. Malan was impressed and Botha was offered a post as party organizer in the Cape. He left the university before completing a degree in order to begin a full-time political career, a decision made when he was only 20 years old. He began working for the National Party as a political organiser in neighbouring Cape Province .
In the years leading to World War II, Botha sympathised with the German Nazi Party. In 1939 Botha, along with T. E. Dönges and J. B. Vorster , helped to form the Cape Town branch of the Ossewabrandwag (Ox-wagon torch guard), where he served as a leader of the organisation. He was nearly interned by the military at one point, because of his pro-German stance. He became disillusioned with the Ossewabrandwag as a result of an internal split and, in August 1941, wrote a scathing letter to Die Burger attacking the organisation.
Botha said that national socialism was ' volksvreemd ', meaning unknown, dangerous and contrary to the Christian nationalism of Afrikaners, and charged the Ossewabrandwag with 'interference' in national politics. He was expelled from the organisation four days later. Soon afterwards D. F. Malan ordered all members of the (NP) to withdraw from the Ossewabrandwag.
On 31 October 2006, Botha passed away at the age of 90 at his house 'Die Anker'. He was found dead in bed just after 20:00 pm by his wife Barbara. A day after Botha's death, the Director-General in the presidency office Rev Frank Chikane visited Botha's family to present an offer for a state funeral and other forms of assistance to this former state president. When responding to the state offer, Mrs Botha said her husband had not wanted a state funeral. "He was not a man that looked for honour and glory," she said. Though his memorial service was opened for public attendance, his burial, was a private occassion. It took place on 8 November 2006 at Hoekwil, a settlement above Wilderness.