Crowds blocked the road and chanted "Keir Starmer's a wasteman" and "What do we want? A ceasefire. When do we want it? Now".
Protesters held up signs saying "Stop the war on Gaza" and waved large Palestinian flags outside the Labour leader's office.
The march began outside Chalk Farm station as part of a day of national action across London and the UK.
Earlier, protesters chanted "from the river to the sea, Palestine will be free" and "free, free Palestine" as they marched towards Camden Town station.
Protesters held signs saying "Who the f*** doesn't vote for a ceasefire?" and "Starmer shame on you" as they walked through the borough.
The Met Police said in a statement on X: "We understand the group plans to stop and gather in Eversholt Street."Officers are present. Their role is to ensure the protest takes place lawfully and safely and that any offences are swiftly dealt with. "If you are there and have concerns, please speak to an officer."
Other protests were planned across London on Saturday and multiple cities across the UK. Police later said the protest in Camden concluded without any incidents or arrests.
Sir Keir has faced fierce criticism over the conflict in Gaza. During the week, 56 MPs defied a three-line whip to back an SNP amendment calling for a ceasefire in Gaza.
Eight frontbenchers, including Jess Phillips, quit the frontbench in order to back the amendment, which was rejected 293 to 125, with a majority of 168.
Among them are four shadow ministers - Ms Phillips, Yasmin Qureshi, Afzal Khan and Paula Barker - along with other frontbenchers Rachel Hopkins, Sarah Owen, Naz Shah and Andy Slaughter.
Parliamentary private secretaries Dan Carden and Mary Foy have also left their positions.