Portman worked with animal rights charity PETA to make the video, which she hopes will make a new generation aware of Singer's legacy.
"Nowadays, many of us speak up for animals, but it wasn't always like this," says Portman in the video. "Decades ago, one man articulated the plight of animals so boldly that the modern world couldn't ignore him."
In the video, Portman says: "Isaac Singer grew up in the same part of Poland as my family. And like them, he fled the horrors of the Holocaust. But the cruelties he witnessed made Singer one of the most powerful writers of the 20th century."
The writer compared the treatment of animals to the treatment of Jews at the hands of Nazis in his autobiographical novel Shosha, writing: "We do to God's creatures what the Nazis did to us."
He also championed women's issues and gay rights (for example, in "Yentl, the Yeshiva Boy") and especially animal rights. "I did not become a vegetarian for my health," Singer once declared flatly. "I did it for the health of the chickens."
Portman made the video with vegan charity PETA
In The Slaughterer, which he wrote for The New Yorker, he tells the story of a young man who loves animals but is appointed his town's ritual slaughterer. Tormented by the cruelty of his actions, the slaughterer ponders the roots of violence.
Singer wrote: "As long as people will shed the blood of innocent creatures there can be no peace, no liberty, no harmony. Slaughter and justice cannot dwell together."
Moby provided music for the video, which was directed by filmmaker Jesse Dylan, whose father, Bob Dylan, was inspired by Singer in the 1960s.