Outside of his diplomatic work, Costos served as a former executive for HBO, and is the current president of film production company Secuoya Studios.

He has served on the board of directors of the Humane Society of the United States, the country's largest animal protection organization.

His initial focus, he said, was on issues of international security and thanking Spain for allowing the U.S. to deploy part of its anti-missile shield defense and for hosting U.S. military bases.

We need a growing Spanish economy to help sustain trade, growth in the EU, and entrepreneurship so that globalization is creating jobs and opportunity for all people, not just a few at the top.” [9] Building on the policy objectives of President Obama to promote global entrepreneurship, Ambassador Costos created and launched an event called InCubed (IN3) in June 2015, where innovators, investors and institutions would meet to network and exchange ideas.

"[10] In October 2013 the Spanish government summoned him to address allegations that the National Security Agency had recently collected data on 60 million telephone calls in Spain.

Mr. Taubman founded PJT Partners in early 2013 and, in October 2014, announced the intention to merge into the spun-off Blackstone advisory businesses.

Ambassador in 2013, the Human Rights Campaign said "Costos is a true citizen of the world, he has incredible global business experience and is a respected and innovative leader.

He has solid business and political relationships at the highest levels and a proven commitment to community, philanthropy, human rights, and democracy that make him an outstanding choice to be the nation's next Ambassador to Spain.” [19] President Biden, in June 2022, appointed Costos to the J. William Fulbright Foreign Scholarship Board, an “educational and cultural exchange” network that connects students and professionals to international graduate and study programs.

"[20] Costos characterized President Trump's handling of COVID-19 as a complete failure, "my country failed the world in this effort by not being adequately prepared for the pandemic and by recklessly refusing to take the lead on a coordinated global response."

He insists that "competent leadership and a firm reliance on science is required to take the necessary actions to save our planet for future generations to come.

"[21] Costos lives in Los Angeles, California, with his partner Michael S. Smith, the official interior designer for the Obama White House.