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 until 1992. He was a Professorial Lecturer of the U.P. College of Law from 1983 until 1992 when he was appointed Chief Presidential Legal Counsel, Office of the President of the Philippines.

Justice Carpio also held other important government positions before assuming office as Supreme Court Justice. He was a member of the Board of Regents of the University of the Philippines from 1993 to 1998. He was a member of the Technology Transfer Board of the Department of Industry from 1978 to 1979. He served as Special Representative of the Department of Trade for textile negotiations from 1980 to 1981. He also served as President of the Integrated Bar of the Philippines Pasay-Makati Chapter (1985-1986), Director of the U.P. Law Alumni Association (1984-1989), and Director of the Philippine Bar Association (1989-1990).

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. 

Justice Carpio is the  Chair of the Second Division and Chair of the Senate Electoral Tribunal.