Justice Carpio obtained his law degree from the College of Law of the University of the Philippines where he graduated valedictorian and cum laude in 1975. He placed sixth in the 1975 Bar Examinations. He earned his undergraduate degree in Economics from Ateneo de Manila University in 1970. In his student days, Justice Carpio was Chairman of the Editorial Board of the Philippine Law Journal of the U.P. College of Law. He was Editor-in-Chief of The Guidon, the school paper of Ateneo de Manila University. He also served as Managing Editor of the Philippine Collegian, the school paper of the University of the Philippines.

Fresh out of law school, Justice Carpio went into private practice and founded the Carpio Villaraza and Cruz Law firm. He was a Professorial Lecturer of the U.P. College of Law from 1983 until 1992 when President Fidel Ramos appointed him Chief Presidential Legal Counsel, with cabinet rank. As such he worked for major reforms in telecommunications, shipping, civil aviation, and insurance industries.

Justice Carpio was a member of the Board of Regents of the University of the Philippines from 1993 to 1998.

In 2001, at the age of 52, he was one of the youngest appointees as an Associate Justice of the Supreme Court. Shortly after his appointment, he launched for the judiciary the Supreme Court e-library, the first full-text searchable and retrievable on-line law library in the Philippines and among the first in Asia.

He penned 935 decisions, 79 dissenting opinions, 30 concurring opinions, 13 separate opinions and 4 concurring and dissenting opinions, leaving no backlog in his docket, a feat rarely attained by a Supreme Court magistrate.

For his “distinguished and exemplary service” to the Republic, Justice Carpio was awarded in 1998 the Presidential Medal of Merit by then President Fidel Ramos. In 1991, Justice Carpio received the Outstanding Achievement Award in Law from the Ateneo de Manila Alumni Association. In 2002, he was also the recipient of the Distinguished Alumnus Award from the Ateneo de Davao Alumni Association. In 2009, he was conferred a Doctorate of Laws, honoris causa, by the Ateneo de Davao University. In 2015, the U.P. Alumni Association named him Outstanding U.P. Alumnus in Public International Law. In 2017, the U.P. Alumni Association again named him one of the three Most Outstanding Alumni of the Association. In 2020, the University of the Philippines conferred on Justice Carpio the Doctor of Laws, honoris causa. In 2021, the Ateneo de Manila University also conferred on Justice Carpio the Doctor of Laws, honoris causa.

Justice Carpio has lectured extensively on the West Philippine Sea issue in various local and international fora. In 2015, the Department of Foreign Affairs sponsored Justice Carpio on a world lecture tour on the West Philippine Sea issue. Justice Carpio presented the Philippines’ perspective on the issue before think-tanks and universities in 30 cities covering 17 countries.

Justice Carpio published his research and analysis of the West Philippine Sea issue in an e-book titled The South China Sea Dispute: Philippine Sovereign Rights and Jurisdiction in the West Philippine Sea.

Justice Carpio was the Chair of the Second Division of the Supreme Court and Chair of the Senate Electoral Tribunal. He retired from the Supreme Court on October 26, 2019 upon reaching the compulsory retirement age of 70.