The event was organised by groups including the Faith Forum and Christian Muslim Forum as a way to "stand with our Muslim brothers and sisters at this time of international turbulence".
Huge turnout in #solidarity & in support of Muslims at first Friday prayers since #QuebecAttack #ProtectEachOther #LondonIsOne #LondonUnited pic.twitter.com/gR1opGfDJ3
— Christian Muslim (@ChrisMusForum) February 3, 2017
It was in response to a terrorist attack on a mosque in Quebec on Sunday evening in which six Muslims were killed.
A gunman opened fire after entering the mosque before fleeing the scene. He then turned himself into police.
Alexandre Bissonnette, 27, was charged with six counts of first-degree murder and five charges of attempted murder on Monday.
The organisers of the event in London said: "We believe that London stands as one and are determined to work peacefully and constructively to ensure Britain follows an open and diverse path."
#LondonIsOne - communities stand together as a mark of solidarity @ReformMovement @LondonChurches @_JasvirSingh @Nadim_Nassar @multifaith pic.twitter.com/hxFEsvrfDF
— Faiths Forum (@LondonFaiths) February 3, 2017
The Bishop of Edmonton Rob Wickham was among the Christians at the event at Wightman Road Mosque.
He told London Live: "There are forces at work trying to drive wedges between communities. We want to come together to demonstrate that together we build a strong community.
Rabbi Laura Janklaus said: "We will form a circle during prayers and this circle will ripple out to show that London - and indeed Britain - stands as one."
Imam Ajmal Masroor said: "We're together. We're against bigotry. We're against prejudice. We're against all sorts of discrimination. The more we do things like this together the more powerful the message becomes."