Hundreds of protesters gathered outside the Labour leader's constituency office in north London calling for a ceasefire in Gaza.
Crowds blocked a road in Camden and chanted "Keir Starmer's a wasteman".
It comes as groups held sit-in protests at several train stations across London.
The demonstrations were part of a day of national action organised by the Stop the War Coalition throughout the UK.
Protesters met outside Chalk Farm station before heading through Camden to Sir Keir's constituency office.
Once there, protesters held up signs with slogans such as "Stop the war on Gaza", "Starmer shame on you" and "Starmer, human rights lawyer? What a joke".
It comes after a vote in the House of Commons calling for a ceasefire in Gaza which saw 56 Labour MPs defy the party line to vote in favour of the motion.
At the event on Saturday, John Rees, national officer for the Stop the War Coalition, told crowds: "You saw what this movement did to Suella Braverman.
"Unless you get yourselves in line with the majority of people in this country who want an immediate ceasefire, this movement will do that to you Rishi Sunak, it will do that to you, Keir Starmer."
The crowds also heard from 33-year-old Palestinian Nida Badawi. She told crowds: "For the past 40 days, over 40 days, I feel like my heart's been ripped out of my body.
"I'm just here to remind you while we're standing here, it's not the time to stay quiet. They need to hear our voices."
Meanwhile sit-in demonstrations took place at various London railway stations, where British Transport Police (BTP) issued Section 14a orders prohibiting protests between 10:00 and 23:00.
Roughly 200 protesters arrived at London Bridge station at about 14:30 GMT and a police cordon was put in place around the station, but BTP later posted on X, formerly Twitter, to say the group had left the area and passengers could access the station as usual.
At Waterloo station, a group of about 100 pro-Palestinian protesters sat down on the concourse demanding a ceasefire in Gaza.
BTP said: "Following engagement with protest liaison officers, protestors are refusing to leave Waterloo station as agreed. Therefore we are moving to arrest phase."
Protesters were removed from the station by officers, with at least two demonstrators carried from the scene.
A protest was also held in Tooting, south-west London, with the Metropolitan Police posting on X that officers worked together with the BTP and "made sure today's demonstration outside Tooting Broadway [station] ended without any incident".