The vigil was also held to demand the release of the 241 people believed to have been kidnapped by Hamas.
Mourners chanted “bring them home” and held posters of the missing.
Prayers were said, with attendees singing in Hebrew.
Following the prayers, a minute’s silence was also held.
Rose, 63, from North West London said she attended the vigil because she was “desperately worried” about the hostages.
“I have been coming to as many of these vigils as possible because I am desperately worried about the fate of around 240 people, Jews, Bedouins and Thai workers.
“They’re all in the gravest of grave danger.
“Probably living in the most unsatisfactory circumstances, and my humanity says we have to fight to save them.
She said that Pro-Palestinian protesters should avoid marching on Armistice Day out of respect for what the anniversary means for “the majority” of Britons.
“I think out of respect for them, and deference for them, I don’t think any other protests should happen that day,” she said.
Alan Mekibel, 28, lives in Israel, but attended the vigil during a two-day visit to London.
“I have friends, I have friends of friends, who have been kidnapped, murdered,” he said.
“And it’s a very non-bi-partisan reality. On the 6th of October there was a ceasefire, there was nothing, on the 7th there was an outright war.”
He said the international reaction to the attack was “scary”.
“How the world is reacting is scary, a man was killed at a pro-Palestinian protest in Los Angeles last night,” he said.
“Schools are being vandalised, my friends are afraid to go to schools in Europe and the United States. It’s not even to show solidarity (this) is what we have to be doing because never again means never again.”