Walker is a fellow of the Institute for Urban Design, a member of the Council on Foreign Relations, and a board member of the Arcus Foundation, Rockefeller Philanthropy Advisors, Friends of the High Line, and the Foundation for Art and Preservation in Embassies. He has been a teacher of housing, law and urban development at the New York University School of Law and the Robert F. Wagner Graduate School of Public Service. He is co-chair of the New York Public Library Council. He is board of directors vice-chairman at the New York City Ballet.
Walker was born in a charity hospital in Lafayette, Louisiana. Walker was raised by a single mother in Ames and later Goose Creek, Texas; and was one of the country's first children to benefit from the Head Start Program. Walker said that his background "has given me an understanding of the need for investment in human capital and the centrality of private philanthropy making a difference in human lives."
With financial support from a Pell Grant, Walker was admitted into the University of Texas at Austin. In 1982, he graduated with a Bachelor of Arts in government and a Bachelor of Science in speech communication. In 1986, Walker graduated from the University of Texas School of Law with a Juris Doctor.
Walker began his career in 1986 at the international law firm Cleary Gottlieb Steen & Hamilton. In 1988, he joined Union Bank of Switzerland (UBS) and spent seven years in its capital markets division.
In 1995, Walker left the corporate world to spend a year volunteering at a school in Harlem. He went on to become the chief operating officer at Abyssinian Development Corporation, a community development organization also located in Harlem. There, he was able to draw on his private sector experience to advance revitalization in Harlem, including the opening of a Pathmark supermarket in 1999 at 125th Street and Lexington Avenue. He also led the development of the first public school built in New York City by a community organization.
From 2002-2010, Walker was vice president for foundation initiatives at the Rockefeller Foundation, where he oversaw a wide range of programs in the United States and internationally. Also, at the Rockefeller Foundation, he led a recovery program in the southern United States in the wake of Hurricane Katrina.
He joined the Ford Foundation in 2010 as vice president for Education, Creativity and Free Expression, one of the foundation's three major program areas. He also oversaw Ford Foundation's regional programming in four offices based in Africa and the Middle East. Walker was involved in securing funding for the American Folk Art Museum when the museum was experiencing financial difficulties.
He served on New York City Mayor Bill de Blasio's November 2013 Transition Advisory Team.
In July 2006, Walker was named the Rockefeller Foundation's vice president for United States and international initiatives.
At Rockefeller Foundation, Walker led the foundation’s work in the United States of America and globally - in terms of supporting innovations that built economic development, sustainability and assets of poor and disadvantaged people; while creating long-term strategies that addressed increasing global migration, movements and urbanization. He also oversaw the Foundation’s new strategy and vision for New York City, including directing Rockefeller Foundation's support of the re-building of New Orleans.
Earlier, from 2002, Walker served as Rockefeller Foundation's working communities program director; where he oversaw a grant making portfolio, in excess of USD$25 million per year, that created anti-poverty strategies focusing on education, employment, sustainable community development, and democracy building in the United States.
Walker was named president of the Ford Foundation in June 2013. He officially stepped into the role of president in September 2013, succeeding Luis Ubiñas.
Walker spearheaded efforts to save DIA: Detroit Institute of Arts and city workers' pensions in the Detroit bankruptcy process. Walker stated that: it was "unprecedented and monumental for philanthropies to undertake this kind of initiative, but if there was ever a time when philanthropy should step up, this is it."
Walker lead nine foundations, many with ties to Michigan - including Community Foundation for Southeast Michigan, William Davidson Foundation, Fred A. and Barbara M. Erb Family Foundation, Ford Foundation, Hudson-Webber Foundation, Kresge Foundation, John S. and James L. Knight Foundation, McGregor Fund, and Charles Stewart Mott Foundation. These US foundations "have pledged to pool the $330 million, which would essentially relieve the city-owned Detroit Institute of Arts museum of its responsibility to sell some of its collection to help Detroit pay its $18 billion in debts. In particular, the foundation money would help reduce a portion of the city’s obligations to retirees, whose pensions are at risk of being reduced in the bankruptcy proceedings. By some estimates, the city’s pensions are underfunded by $3.5 billion." Walker's Ford Foundation pledged to provide USD$125 million for the USD$330 million common fund from the nine Foundations.
In January 2014, with Alberto Ibargüen, Mariam Noland and Rip Rapson, Walker, in The Chronicle of Philanthropy, explained their reasonable motivation for the commitment to help the people of Detroit in this tragic period:
"Tens of thousands of Detroit’s public servants face deep cuts to their retirements and livelihoods. Shoring up the pension funds helps these families, strengthens the local economy and relieves some of the pressure on the city’s operating budget. Similarly, the proposal would safeguard the DIA, a treasured cultural beacon that for decades has helped strengthen the Detroit metropolitan area, attracted residents and visitors alike, and added to Detroiters’ sense of identity and connection to the city. Our support also aims to accomplish something even larger: helping a great city get back on its feet quickly and on course toward a better future. This new investment, above and beyond our existing grant making in the region, represents our desire to seize a rare opportunity and play a constructive role in the revitalization of Detroit.
We see a one-of-a-kind chance to make an investment that is true to all of our values and our giving priorities and that embodies the kind of flexible, creative, and transformative philanthropy we believe in. At its best, we hope our involvement may bolster the spirit of positive engagement and creativity in Detroit, catalyzing others to invest strategically across the region. It does not mark the start of philanthropy as a solution to public insolvency. This is a unique, clear-eyed move to push forward positive negotiations, with our philanthropic dollars being exclusively pegged for two roles: safeguarding the DIA and protecting pensions.