The death of father-of-six Makram Ali and the injury of a dozen others on 19 June last year will be commemorated with a minute’s silence.
Mr Ali’s relatives have been invited to gather along with others affected when far-right attacker Darren Osborne drove a hire van onto a crowded pavement intending to kill as many Muslims as possible.
Home Secretary Sajid Javid and London Mayor Sadiq Khan are due to attend the event at Islington Town Hall on Tuesday, where a silence will be held at 9.30am.
During his trial at Woolwich Crown Court, Osborne named Mr Khan as someone, along with Labour leader Jeremy Corbyn, he had wanted to kill.
Islington councillors, local faith and community leaders, and emergency services workers who helped victims after the attack are set to attend the commemoration.
The prime minister said: “Last year’s cowardly attack which targeted innocent worshippers leaving Finsbury Park mosque is an attack on all of us.
“As with all acts of terrorism the intention was to divide us but we will not let this happen.
“We are a country of many faiths and freedom of worship and respect for those of different faiths is fundamental to this country’s values and these values will never be broken by vile extremism.”
The prime minister praised the “bravery and spirit of the community that apprehended the attacker”.
She added: “As we remember the victims of this attack, Makram Ali who tragically lost his life, we should take strength that it is London’s diversity and multitude of communities that makes it one of the world’s great cities.”
At a gathering earlier this month, Mr Ali’s daughter Ruzina Akhtar spoke of her family’s gratitude for the support they had received from the community since her father’s death.
Ms Akhtar addressed those gathered at a street iftar on what was the one-year anniversary of the incident, according to the lunar calendar observed in the Islamic faith.
She said: “We’re very happy to be part of this community and to be in this country with such a loving, diverse community around us.
“And we would just like to thank everyone for their support and the love that they’ve shown and hope they continue to do so.”
The phrase #LondonUnited, which has been used following other terror attacks in 2017, was due to be displayed on the Muslim Welfare House on Monday evening and into the early hours of Tuesday, around the time Osborne committed his crime.
Jobless Osborne, who had been radicalised by far-right material, was jailed at least 43 years after being found guilty in February of murder and attempted murder.