Mills was born on 21 July 1944 in Tarkwa, in the Western Region of Ghana.^[1] His parents were John Atta Mills, Sr., an educator, who taught at the Komenda Teacher Training College and Mercy Dawson Amoah.^[3] He was the second child (and first son) among seven siblings.^[3] A member of the Fante ethnic group, he hailed from the town of Ekumfi Otuam in the Mfantsiman East constituency of the Central Region of Ghana.^[4] He had his primary and middle school education at Huni Valley Methodist Primary School and Komenda Methodist Middle School respectively.^[5][6] He then proceeded to the prestigious Achimota School for his secondary education, where he completed the Ordinary and Advanced-Level Certificates in 1961 and 1963 respectively, and the University of Ghana, Legon, where he completed a bachelor of law degree, LLB and a professional law certificate in 1967.^[1][7]

Mills studied at the London School of Economics and Political Science where he obtained an LLM in 1968 and earned a PhD in Law at the School of Oriental and African Studies School of Law, part of the federal University of London,^[8] after completing his doctoral thesis in the field of taxation and economic development in 1971 at the age of 27. Even during his career in politics, he was sometimes called by the nickname The Prof, a reference to his long academic career.^[1] His political supporters also called him Asomdweehene meaning 'King of Peace' in the Akan language.^[1]