The royal joined the families of the victims, survivors, first responders, and other emergency workers.
'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'.
On May 22 a year ago, a terrorist detonated an explosive device as fans were leaving Grande's concert at the Manchester Arena, killing 22 innocent people and injuring more than 500.
Tuesday's remembrance service was also shown on a big screen in nearby Cathedral Gardens, as well as at churches in York, Liverpool and Glasgow.
Twenty-three people including the attacker were killed in the terror attack at an Ariana Grande concert.
In a message on social media, the American singer wrote: "Thinking of you all today and every day". A total of 22 people were killed and more than 800 others were either physically or psychologically injured.
Following the attack, Grande put on a benefit concert in Manchester for the families of those affected.
Some 7,000 knitted and crocheted hearts were also dotted around the city centre while a trail of 28 Japanese maple trees had been planted in compost made from last year's memorial flowers leading from the station to the Cathedral Gardens for people to hang "message of hope" on their branches. I think today it's important to remember the power of the One Love gig and how it brought not just the city but the world together.
Later Tuesday, more than 3,000 singers from local choirs will come together to mark the anniversary in Albert Square.
The first time you go into Manchester as a kid, you're just so excited.
"Today my thoughts and prayers are with those who were lost on that bad night, their loved ones who have so bravely battled to rebuild their lives; those who have courageously fought to overcome physical injury or mental scars; our first responders and emergency services and those volunteers and professionals who are continuing to help this community heal", May wrote. Because we know what is to come, all images of the concert seem like grim foreshadowing, from the stylised silver teardrops on the face of the performer to the explosions of the beat or the screams of the crowd. "The country stood strong, especially Manchester". They sang Andra Day's Rise Up, which got half the audience blubbing when a little boy on the front row ran for a cuddle from the choir leader before the track got going.
They included Don't Look Back in Anger by Oasis, One Day Like This by Elbow and Never Forget by Take That. Instead 100 pedestrians and a handful of transport police who rushed to the scene improvised, with T-shirts for tourniquets and crush barriers for stretchers.