He also dug into Trump's domestic economic plans, ripping his proposed tax cuts for the wealthy.
"Trump's big economic plans: Give trillions in tax breaks to millionaires, refuse to raise the federal minimum wage," Sanders summarized.
While Trump has made a conscious effort to appeal to Sanders supporters who feel that Hillary Clinton is part of the problem, Sanders has frequently dismissed the idea that his supporters would back Trump.
"Those who voted for me will not support Trump who has made bigotry and divisiveness the cornerstone of his campaign," Sanders wrote. "We believe in bringing people together, not dividing them up."
During his unexpectedly successful run for the presidency, Sanders heavily emphasized soaring income inequality and declining opportunity for American workers who have been left out of an economy that handsomely rewards those at the very top.
While Trump, as a billionaire who has used his economic clout to take advantage of the political system, wouldn't immediately strike one as a convincing populist, his "America First" message of nationalism and his strongman approach to both foreign and domestic affairs has cultivated a wide base of support among the American public.
Sanders, however, has urged working Americans to view Trump as a man who is cynically using a message of xenophobia to take advantage of the economic anxieties of millions of Americans. Sanders has also stressed the need for political movements, noting that one politician cannot alone solve the nation's crises.
Trump, Sanders notes, has taken the opposite approach, posing as a kind of savior.
Quoting Trump as saying, "I alone can fix this," Sanders pointedly asked, "Is this guy running for president or dictator?"
Sanders also placed emphasis on what Trump didn't say, observing that these issues are some of the most important we face.
"Will there be one word about student debt or making college affordable?" Sanders asked. "Citizens United is one of the worst decisions in our history. Will Trump mention it or is he too afraid of the Koch brothers?"
If one word could summarize Sanders's assessment of Trump's performance, it would be the one he added to the end of yet another critique of Trump's economic platform.
"Trump's economic plan: same old, same old trickle-down economics. Pathetic."