After graduating, Gamalinda worked as a reporter for various newspapers and magazines in the Philippines. He also wrote for several foreign publications, including The Wall Street Journal, The New York Times, and The Washington Post.
In 2001, Gamalinda published his first book, "Islands in the Stream: Journeys with the Philippine Marine Corps in the Sulu Archipelago". The book won the National Book Award for Nonfiction and was also shortlisted for the Pulitzer Prize.
Gamalinda has since published several other books, including "American Colonialism in the Philippines" (2004), "The Last Revolution: The First Hundred Days of the Aquino Administration" (2010), and "The Philippines in the Twenty-First Century: A Nation on the Cusp of Change" (2015).
In addition to his writing, Gamalinda has also worked as a consultant for various government and non-government organizations. He has also taught journalism at the University of the Philippines Diliman and the Ateneo de Manila University.
Gamalinda is a recipient of several awards, including the Ramon Magsaysay Award for Journalism (1999) and the Nieman Fellowship (2001). He is also a member of the Order of the National Artists of the Philippines.