Kwa Geok Choo was the daughter of Kwa Siew Tee, former general manager of Oversea-Chinese Bank and Singapore Municipal Commissioner. Kwa attended Raffles Institution and Raffles College, and according to Lee Kuan Yew's memoirs, by 1939, Kwa and Lee were both top students, often coming first and second in exams. They continued their courtship during the Japanese occupation, and after the war when Lee was in Cambridge, he petitioned for Kwa to be admitted to Girton College, saying she was "a very bright girl, brighter than I was". Kwa married Lee in secret in London in 1947 and then remarried in Singapore on September 30, 1950. They had two sons – Lee Hsien Loong and Lee Hsien Yang – and a daughter – Lee Wei Ling. Her brother, Kwa Soon Bee, served as a Permanent Secretary in the Ministry of Health. She had three sisters: Mrs Cheah, a teacher at Methodist Girls' School; Mrs Yong, the wife of Yong Nyuk Lin; and Mrs Earnest Lau, who was also a teacher at Methodist Girls School.
During Lee's years as Prime Minister and Senior Minister, Kwa was frequently seen with her husband, especially on diplomatic trips and meetings with other foreign ministers. After suffering two strokes in May and June 2008, she was bedridden and unable to speak, but remained conscious and able to understand speech.
When Singapore separated from the Malaysian Federation, Kwa drafted the clauses in the Separation Agreement for the guarantee of the water agreements between the Malaysian state of Johor and Singapore. This guarantee was done via an amendment to the Federal Constitution of Malaysia.
It is also notable that before Singapore's merger with Malaysia, Kwa had told Lee Kuan Yew that she did not feel positive about the merger. Her gut feelings were later proven true when the merger fell through shortly after it was passed.
Kwa was also a pioneer advocate of women's rights in Singapore.
Kwa died in her sleep at home, following a long illness on 2 October 2010 around 0540 hours SST. She was given a state funeral and cremated at Mandai Crematorium on 7 October 2010.
In 2011, the Singapore Management University named its new law library, a new scholars programme and a top law graduate award after Kwa. In the same year, the National University of Singapore established a professorship in property law, a distinguished visitors programme, bursaries and scholarships in her honour. Nanyang Girls' High School also unveiled a bust of Kwa at its Yu Zhi Library, which is named after her.
Singapore's Peranakan Museum currently displays Kwa's barrister wig on its third floor.
In 2011, former Far Eastern Economic Review comic artist Morgan Chua released In Memory of Kwa Geok Choo (1921-2010), a book of sketches and political cartoons in tribute to her.
In October 2014, the Madame Tussauds Singapore museum unveiled wax figures of Kwa and Lee Kuan Yew seated and smiling together against a backdrop of red flowers formed in the shape of two hearts. The statues were created based on a photograph that was taken by Kwa's niece, Kwa Kim Li, of the pair on Valentine's Day in 2008 at Sentosa.
In the same month, Cultural Medallion recipient Tan Swie Hian completed a painting of Kwa and Lee Kuan Yew entitled A Couple. The painting, which took Tan five years to complete, was partially damaged by a fire in 2013. It depicts Kwa and Lee in their youth, is based on a 1946 black-and-white photograph of the couple in the University of Cambridge, and incorporates in its background Tan's poem written in memory of Kwa. Tan said, "I have always felt [Madam Kwa] was a great woman who, despite her intelligence and capability, was also a humble and dedicated wife." A Couple was purchased by art collector Wu Hsioh Kwang. Philippines: Golden Heart Presidential Award (15 January 1974)