The liberal senator has said he is "prepared to work" with Trump but will "vigorously oppose him" if he pursues racist and sexist policies. Other US progressives like Elizabeth Warren have echoed Sanders' sentiments.
He acknowledged that Trump "tapped into the anger of a declining middle class that is sick and tired of establishment economics, establishment politics and the establishment media."
Sanders said that if Trump is serious about enacting policies which seek to improve the lives of working families, "I and other progressives are prepared to work with him."
That offer, however, did not come without a few strings attached. Should the President-elect pursue "racist, sexist, xenophobic and anti-environment policies, we will vigorously oppose him."
Sanders also landed a dig on Trump in his Facebook statement, saying how "people are tired...of billionaires not paying any federal income taxes."
A New York Times report in October found that Trump is estimated to have avoided paying millions of dollars in personal income tax. During a presidential debate with Clinton, he said his tax-avoidance tactics made him "smart."
Sanders ran against Clinton for the Democratic Party nomination, but supported her as a presidential candidate after she won.
The primary race between the two candidates was particularly bitter, with Sanders garnering a great deal of support from young voters who supported his calls for income equality and free education.
Warren's 'sincere hope' to Trump
Massachusetts Senator Elizabeth Warren said it was "no secret" that she didn't want Trump to win the election. But the progressive politician also proposed that she and Trump "put aside our differences" to rebuild the US economy for working people in a statement on Wednesday.
Warren said it was her "sincere hope" that Trump will serve all Americans "no matter who they are, where they come from, what they believe, or who they love."
Warren, a favorite with liberals and a Clinton supporter, has traded harsh words with Trump throughout the campaign. As recently as Monday, Trump called the Massachusetts senator a "terrible human being" and a "terrible senator."
Trump's surprising win early on Wednesday sparked protests in cities across the nation, with many demonstrators angered by Trump's campaign comments about minorities, Muslims and women as well as his anti-immigration stance.
In October, Trump delivered a speech where he laid out his plans for his first 100 days in office. In the address, he said he would repeal and replace Obamacare, as well as allow the controversial Keystone pipeline to proceed and revive the coal industry.
He has also called for a ban on Muslim immigration as well as for deportations of undocumented Mexican migrants. The President-elect also came under fire after a video leaked in October of him bragging about sexually assaulting women.
Environmental reactions to Trump victory
Trump has made no secret of the fact that he does not believe in climate change, and that global warming is a hoax. Read what environmentalists and climate fighters are saying about his election victory.
Image: picture-alliance/dpa
Gray zone
"Trump must choose whether he will be a President remembered for putting America and the world on a path to climate disaster, or for listening to the American public and keeping us on a path to climate progress. Trump better choose wisely, otherwise - we can guarantee him the hardest fight of his life every step of the way.” - Michael Brune, Executive Director, The Sierra Club
Image: picture-alliance/dpa
Dry reality
"Today is a bad day for international climate policy. That a climate change denier can be elected as the most powerful man in the world will make efforts to reduce emissions and secure adequate funding for adaptation measures all the more difficult... The international community needs reliable partners for ambitious climate policies." - Sabine Minninger, climate advisor for Brot für die Welt
Image: Getty Images
Out of control
"The Paris Agreement was signed and ratified not by a President, but by the United States itself. As a matter of international law, and as a matter of human survival, the nations of the world can, must, and will hold the United States to its climate commitments." - Jean Su from California-based Center for Biological Diversity
Image: picture-alliance/AP Photo/K. Salzmann/US Forest Service
Green solutions
"We know that yesterday's elections are undoubtedly going to affect the tone of the negotiations, but we know the task we have in front of us remains the same: that we must continue to keep our aim and our focus on the long-term that the countries set for themselves in the Paris Agreement." - Mariana Panuncio-Feldman, World Wildlife Fund's (WWF) Senior Director of International Climate Cooperation
Image: Getty Images/R.Wise
Slow death
"For communities in the global south, the U.S. citizens' choice to elect Donald Trump seems like a death sentence. We are suffering the effects of climate change after years of inaction by rich countries... and with an unhinged climate change denier in the White House, the relatively small progress made is under threat." - Wilfred D'Costa, Asian Peoples' Movement on Debt and Development
Image: picture-alliance/dpa/C. Melzer
Opening the floodgates
"President-elect Donald Trump's stance on global warming is well known. Ironically, he contributed to the popularity of our recent 'Turn down the heat'-report series for the World Bank by attacking it on Twitter. Yet apart from this, science cannot expect any positive climate action from him." - Hans Joachim Schellnhuber, Director of the Potsdam Institute for Climate Impact Research
Image: Reuters/D. Reuter
Washed up?
"It's clear that Donald Trump is about to be one of the most powerful people in the world, but even he does not have the power to change the laws of physics... Climate change has become a geopolitical issue of the top order and no country can be perceived as not doing its fair share on climate without serious consequences for its standing in the world." - Alden Meyer, Union of Concerned Scientists
Image: Reuters/T. Kalifa
A burning issue
"As a young woman and first-time voter I will not tolerate Trump's denialism of the action needed for climate justice. Our country must undergo a systemic change and just transition away from fossil fuels towards renewable energy within my lifetime. The next four years are critical for getting on the right pathway." - Becky Chung, the youth network SustainUS.
Image: Getty Images/AFP/J. Edelson
Time to be clean
"The fact of climate change is not changed by what happened last night. At this very historic moment, it is important to remind ourselves that we were in the wilderness before and progress was possible. Leaders across the world will expect the US to honor its commitment and they won't wait in the race to the renewable energy future." - Li Shuo, Greenpeace China
Image: picture-alliance/dpa
Shrinking opportunities
“Donald Trump is the newly elected President of the United States. As of today, the Paris Agreement is an even stronger signal against denying reality and for global cooperation to solve the pressing problems of the world... You cannot ignore the facts." - Christoph Bals, Policy Director of Germanwatch
Image: Getty Images/M.Ralston
Powerful force
“Trump will try and slam the brakes on climate action, which means we need to throw all of our weight on the accelerator... We need the rest of the world to charge ahead and look beyond the White House to partner with civil society, businesses, and local governments who are still committed to climate action... Our work becomes much harder now, but it’s not impossible.” - 350.org
Image: AP
Growing concern
"Africa is already burning. The election of Trump is a disaster for our continent. The United States, if it follows through on its new President's rash words about withdrawing from the international climate regime, will become a pariah state in global efforts for climate action." - Geoffrey Kamese from Friends of the Earth Africa