The High Fidelity star shared a meme of a large hand with the Star of David on its wrist oppressing a group of people with a caption that read: “To learn who rules over you, simply find out who you are not allowed to criticise.”
The saying is often attributed to the French philosopher Voltaire but was actually spoken by white nationalist Kevin Strom.
Cusack, 52, added “follow the money” to the meme but deleted his post when it sparked criticism.
He said he had believed the tweet related to an Israeli hospital bombing and had “mistakenly retweeted an alt-right account”.
Cusack said: “It’s clear that even if it was Israel’s flag & even if you don’t have anti-Semitic bone in your body, it is still an anti-Semitic cartoon. Because it deploys anti Jewish stereotypes.
“I [retweeted] and quickly deleted an image that’s harmful to both Jewish and Palestinian friends, and for that I’m sorry.”
He also said he had been victim of a Twitter bot, saying: “A bot got me. I thought I was endorsing a pro Palestinian justice retweet of an earlier post. It came I think from a different source. Shouldn’t have retweeted.”
Jewish writer Elad Nehorai asked: “How does a bot ‘get you to write ‘follow the money’ after sharing an overtly anti-Semitic image?”
English comedian David Baddiel, also Jewish, said: “John Cusack says he didn’t at first realise that the image was anti-Semitic. My, it’s a troublesome old blind spot for progressives, isn’t it?”