Concepcion started as faculty of Siena College in 1985. He served as Bar reviewer in Corporation and Civil Law at the UP Law Center Bar Review School and bar reviewer in Civil Law at the San Sebastian CollegeSchool of Law and Adamson University College of Law. After serving as President of De La Salle Araneta University, he returned to UP in 2002 to become Associate Dean of the UP College of Law, Head of the UP Law Center and Director of the Institute of Judicial Administration until May 2006. He was appointed as Vice-President for Legal Affairs of the University of the Philippines in February 2011 and was elected as the 14th Dean of the UP College of Law on June 3, 2011.
Government Service
Concepcion served as member of the Sangguniang Bayan of Valenzuela and President of the Kabataang Barangay Federation of Metro Manila from 1976 to 1978. He was elected as the Youth Sector representative in the Interim Batasang Pambansa from 1978 to 1984. He also served as member of the Philippine delegation to the Asia Pacific Parliamentarian's Union Conference held in Republic of Nauru in 1979, Vice chairman of the Philippine Youth delegation to the People's Republic of China in 1979, and member of the Philippine delegation to the Inter-Parliamentary Union Spring Conference in Lagos, Nigeria in 1982. He served as Chief of Staff of the Chief Presidential Legal Counsel Office of the President in 1996 as well as associate commissioner of the Securities and Exchange Commission from 1996 until his resignation in 2000 to serve as President of De La Salle Araneta University.
Law Practice
He served as corporate receiver of Daikin-Alen Air Corditioning, Inc., Rehabilation receiver of Ariel Meat Products; Epixtar, Inc.; Capital Wireles, Inc.; Reynolds Inc. and as Securities and Exchange Commission commissioner-in-charge of the rehabilitation of the Victorias Milling Corporation. He is presently serving as a member of the editorial board of the IBP Law Journal, arbitrator in the Ad Hoc Arbitration cases with the Philippine Dispute Resolution Center, Inc., Liquidator of several companies National Steel Corporation; Bacnotan Steel Industries, Inc.; EYCO Group of Companies; Rubberworld, Inc.; East Asia Capital; Winsource Solutions, Inc.; Advent Capital Corporations; PET Plans, Inc. Corporate Counsel of Gordon Dario Reyes Hocson & Viado Law Office and of Tan & Concepcion Law Firm.
As UP President
In 2016, the UP Board of Regents elected Concepcion for the role as president. Other nominees included Gisela Concepcion, Rowena Cristina Guevarra,, Benito Pacheco, Prospero de Vera III, and Caesar Saloma. In August 2018, a reunion of the Kabataang Barangay led by Imee Marcos was held in the University of the Philippines Diliman, which Concepcion attended as a former KB chairman. His presence provoked criticism from opponents of the Marcos regime. As a response, Concepcion has expressed regret and apologized to the UP community while reassuring his commitment to upholding the truth in the harm caused by Martial Law during the Marcos Regime. Concepcion was president of the KB Federation in Metro Manila from 1976 to 1978.