The Heising-Simons Foundation primarily funds organizations that work on environmentalist policy, climate change, scientific research, education, and human rights issues.  Since its founding in 2007, the foundation has donated more than $618 million to these causes. In 2019 alone, the Foundation awarded over $113 million in grants. 
Liz Simons is the chair of the board of directors of the Heising-Simons Foundation.  Simons is the daughter of billionaire hedge fund manager and liberal philanthropist James Simons. James Simons is the founder of Renaissance Technologies, a prominent hedge fund that pioneered the use of quantitative models and statistical analysis in financial investing during the 1980s. In the 1990s, James Simons founded the Simons Foundation to fund left-of-center causes and provide research grants for the study of life sciences, physical sciences, and mathematics. The Simons Foundation is one of the wealthiest foundations in the country. 
In 2017, left-wing British newspaper The Guardian published a story alleging that James Simons had hidden $8 billion in Bermuda, possibly to avoid taxes in the United States. The “Paradise Papers” leak showed that Simons had established sub-trusts in the country for himself and each of his children. Internal Revenue Service (IRS) filings from 2011-2012 show that Liz Simons transferred $54 million from her Bermuda sub-trust to the Heising-Simons Foundation. 
Liz Simons sits on the board of the Learning Policy Institute, a left-leaning education policy research organization. She also sits on the board of the Foundation for a Just Society, a private foundation founded by her half-sister, Audrey Cappell, that funds left-of-center organizations to advance LGBT interests internationally.  Simons’s brother, Nathaniel Simons, is the founder of the Sea Change Foundation, a left-of-center private foundation that funds climate change and clean energy causes.
Mark Heising is a vice chair of the board of directors of the Heising-Simons Foundation. Heising sits on the board of directors of Renaissance Technologies.  He is also the chairman of the Environmental Defense Fund, a nonprofit environmentalist group known for its left-of-center political agenda and advocacy surrounding global warming. Heising also sits on the board of the Bipartisan Policy Center, a center-left think tank headquartered in Washington, D.C. 
Heising and Simons have given hundreds of thousands of dollars to the Democratic Party. In 2020 alone, Heising gave more than $500,000 to the Democratic National Committee, $70,000 to the Democratic Congressional Campaign Committee, $70,000 to the Democratic Senatorial Campaign Committee, and over $350,000 to Joe Biden’s Presidential campaign.  That same year, Simons gave $300,000 to the House Majority PAC, an unlimited-expenditure “Super PAC” associated with Democratic leadership in the U.S. House of Representatives. 
Simons and Heising’s daughter, Caitlin Simons, is a vice chair of the board of directors of the Heising-Simons Foundation. Caitlin Simons also sits on the board of directors of Human Rights Watch, an international non-governmental organization that conducts research and advocacy on human rights. Caitlin Simons is also on the advisory council of the Responsible Business Initiative for Justice, a United Kingdom-based criminal justice advocacy organization. 
Danna Gomby is the president and chief executive officer of the Heising-Simons Foundation. Gomby previously worked for the David and Lucile Packard Foundation, a private foundation that supports left-of-center environmental causes and population control programs. 
Jeff Malloy is the chief operating officer of the Heising-Simons Foundation. Malloy previously worked for the James Irvine Foundation, a donor organization that has given to various left-of-center labor union activist organizations, anti-energy organizations, and immigration advocacy groups. 
Kelly Hayashi is the director of grants management at the Heising-Simons Foundation. Hayashi previously worked at the Stuart Foundation, a left-leaning grantmaking foundation that focuses on education in the state of California. 
Cynthia Atherton is the director of the science program at the Heising-Simons Foundation. Atherton previously worked for the Gordon and Betty Moore Foundation, a grantmaking foundation that funds left-of-center environmentalist organizations. 
Barbara Chow is the director of the education program at the Heising-Simons Foundation. Chow previously worked for the William and Flora Hewlett Foundation, the sixth wealthiest foundation in the country. Chow also previously worked in the Clinton administration as Deputy Director of the Domestic Policy Council and Special Assistant to the President for the White House Office of Legislative Affairs. Before working in the executive branch, Chow worked for the Senate Democratic Policy Committee. 
The Heising-Simons Foundation is a member of We Are Still In, a left-of-center coalition that supports the Paris Climate Accords, an environmentalist agreement negotiated by the Obama administration from which the Trump administration pulled out of in 2017. 
The Heising-Simons Foundation is a member of the Fund for a Safer Future, a gun control advocacy organization and coalition run by the New Venture Fund.  The foundation is also a member of the Hope and Heal Fund, another gun control organization run by the New Venture Fund. 
The Heising-Simons Foundations funds a number of left-of-center organizations. In 2018, the foundation gave to a number of prominent left-leaning donor groups including the New Venture Fund; the Tides Foundation; Rockefeller Philanthropy Advisors; the Bill, Hillary, and Chelsea Clinton Foundation; the Environmental Grantmakers Association; NEO Philanthropy; the Groundswell Fund; and Borealis Philanthropy. 
Also in 2018, the foundation gave to a number of left-of-center think tanks and advocacy groups, including the Center for American Progress, the Urban Institute, the New America Foundation, the National Committee for Responsive Philanthropy, the National Consumer Law Center, and the Environmental Defense Fund.