Elie Lemmel said he was sitting at a cafe in the Paris suburb of Neuilly-sur-Seine on Friday when he was hit in the head by a chair.
"I found myself on the ground, I immediately felt blood flowing," he said.
He was stunned and unsure what exactly had happened, he said, initially thinking something must have fallen from a window or roof, before it occurred to him he had been attacked.
"Unfortunately, given my beard and my kippah, I suspected that was probably why, and it's such a shame," he said.
Friday's incident follows another in the town of Deauville in Normandy last week, when Lemmel said he was punched in the stomach by an unknown assailant.
Lemmel said he was used to "not-so-friendly looks, some unpleasant words, people passing by, spitting on the ground," but had never been physically assaulted before the two attacks.
The prosecutor's office in Nanterre said it had opened an investigation into the Neuilly attack for violence aggravated by the fact that it was committed on religious grounds.
A man being held for questioning at the Neuilly-sur-Seine police station underwent a psychiatric examination that required his hospitalization, it said.
According to German-language identity documents found in his possession, the 28-year-old suspect was born in Gaza's Rafah.
"This act sickens us," former Prime Minister Gabriel Attal wrote on X regarding Friday's incident involving Lemmel. "Antisemitism, like all forms of hatred, is a deadly poison for our society."
Last week, five Jewish institutions were sprayed with green paint in Paris.
"Attacking a person because of their faith is a shame. The increase in anti-religious acts requires the mobilization of everyone," Interior Minister Bruno Retailleau said on X.
France has seen a rise in hate crimes. Last year, police recorded an 11% rise in racist, xenophobic or antireligious crimes, according to official data published in March. The figures did not include a breakdown by attacks on different religions.
