The Love Island host died by suicide at the age of 40 in February 2020.
A year on, a trailer has been released for the one-off special, titled Caroline Flack: Her Life and Death.
It shows various clips of the star over the years, with one emotional moment showing her crying and saying: ‘The only person I ever hurt is myself.’
The trailer sees Flack’s mother, Christine, say: ‘She was my little girl. It doesn’t actually seem real.’
Her twin sister Jody, and her Xtra Factor co-star Dermot O’Leary also appear in the trailer, speaking about their memories of her.
As clips of the presenter play during the trailer, a voiceover says: ‘One year on from her tragic death, we pay tribute to one of Britain’s biggest stars, revealing the complex woman behind the TV persona.
‘Her story, told by those who knew her best.’
The documentary, which is set to focus on the struggles the late presenter faced, was announced last year.
Lee McMurray, who commissioned the programme, said: ‘After working closely with Caroline throughout 2019, we agreed to make a film with her that would tell her story and reveal what it’s like to live in the glare of such intense scrutiny.
‘Sadly, that film will never be made. We hope this project will be a testament to Caroline’s character, work and legacy, and we’re deeply grateful to her family and friends for their involvement.’
Flack died by suicide at the age of 40, with friends and fans remembering her a year on from the tragedy.
Her ex-boyfriend Lewis Burton, who she was dating at the time of her death, shared a selfie he took with the TV star and wrote: ‘1 year… I will never forget you,’ along with full and broken heart emoji.
Flack’s former fiance Andrew Brady also penned a lengthy tribute on a WordPress page, which said in part: ‘Tomorrow is the one-year anniversary of Caroline’s death, the person I loved more than anyone I ever thought possible.
‘Not a day goes by that I don’t think of her, I have some truly incredible memories of her etched on to my mind for eternity.’
Other tributes have begun pouring in for Flack, with a post on the ITV2 Twitter account featuring a Love Island photo of the presenter and the caption: ‘Remembering Caroline 1979-2020. Always in our hearts.’
Laura Whitmore, who took over hosting Love Island following Flack’s death, shared heartfelt song lyrics on Instagram, which read: ‘You’ve got to laugh a little, cry a little, until the clouds roll by a little.’
Caroline Flack: Her Life and Death will air soon on Channel 4.