The service included first responders, survivors and the families of those involved in the attack.
HRH The Countess of Wessex and several church and government officials attended the service, including the Mayor of London, Sadiq Khan, the Home Secretary, Amber Rudd, and Cardinal Archbishop of Westminster, Vincent Nichols.
The Archbishop of Canterbury, Justin Welby, preached a sermon on the effects of the tragic events.
He said: "As we see you, as we see this area with its constant memories of what has happened, we seek to share with you in a way that reminds you that you are not alone, that the pain you suffer is not considered passing but profound, and that the grief for the lost is something that will forever be inscribed by our memories in these very stones, stones that over so many centuries have seen so much violence, but have also seen the renewal of hope and the overcoming of evil.
Welby also honoured first responders.
He added: "To those especially who are here from the first responders we say this: your dedication, courage and effectiveness are beyond measure.
"This was the second event in London, which we might hope only to see once in a generation."
Children from the Cathedral School of St Saviour and St Mary Overie lit candles – one for each of those who had died and a moving Act of Remembrance and Commitment was led by the Bishop of Southwark, The Rt Revd Christopher Chessun, together with representatives of the faith communities.
Bishop Christopher said: "Since the attack this community has been united in solidarity.
"It is important that we remain committed to working together with our friends from other faith communities and each other to ensure that we build a resilient society in which all are welcome and none feel excluded, so that we can truly pursue justice, show mercy and seek peace."
