The cathedral service was shown on a big screen in the city as well as in other cities across Britain, including York, Liverpool and Glasgow.
Later Tuesday, more than 3,000 singers from local choirs will come together to mark the anniversary in Albert Square.
There was also a mass sing-a-long of Ariana Grande's hit "One Last Time", which you can see below.
Among the dignitaries present were the Duke of Cambridge, Prime Minister Theresa May, Labour Party leader Jeremy Corbyn, First Minister of Scotland Nicola Sturgeon, Lib Dem leader Sir Vince Cable, Greater Manchester Chief Constable Ian Hopkins, Greater Manchester Mayor Andy Burnham and Sir Richard Leese, the leader of Manchester City Council.
The singer had just finished performing and concert-goers were leaving the arena when 22-year-old Salman Abedi blew himself up in the building's foyer. "I love you with all of me and am sending you all of the light and warmth I have to offer on this challenging day", she wrote along with a worker bee emoticon which is widely used to represent the city as a symbol of industry.
The ceremony included a national silence at 2.30pm to allow the country to remember those who died.More news: Nord Stream 2 gas pipeline raises intelligence concerns say US
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22 people were killed in the atrocity on 22 May, 2017.
Around an hour and a half later, at 10.31pm, bells on Manchester Town Hall, St Ann's Church, and St Mary's RC Church rang to mark the time the bomb went off one year ago.
Prince Harry, carrying out his first public engagement as a married man, also remembered the victims during a speech in London.
Last night's evening of solidarity through music began with a series of video messages from some famous names, including many Mancunians. Thinking of the 22 who lost their lives and those who lost loved ones.
Flowers left by people as they pay their respects in St Annes Square on the 1st anniversary. Others left hand-written notes on Japanese maples that have been planted to form a "Trees of Hope" trail through the city. More than 7,000 handmade stitched hearts have also been dotted around the city centre, with people encouraged to smile on the day.