The former Strictly star revealed the extent of her injuries and explain the psychological toll it had on her life.
She was left blind in one eye and suffered severe burns to most of her face after her ex-boyfriend hired a man to chuck the substance at her in 2008.
To mark World Mental Health Day, the presenter shared the previously unseen photo, thought to have been taken shortly after the assault.
Writing alongside it, Katie, 35, said: "I remember when I didn’t want to look at anyone. I remember when I didn’t want anyone to look at me.
"I remember when I was scared of people, scared of men. I remember when I was scared of the world.
"I remember when opening up to people and talking about my trauma and psychological damage just wasn’t possibly.
"Today on Mental Health Day my first meeting of the day is with my therapist. I still go, it still helps and I’m able to talk."
Sharing some final words for those in need of some help, she added: "Hold On Pain Ends," along with hashtags raising awareness for mental health.
Katie was flooded with messages of support from her followers who described her as a "hero" and an "inspiration to so many people".
The model and philanthropist recently took part in the Every Mind Matters campaign, with Meghan Markle, Prince Harry, Prince William and Kate Middleton.
Last year, she revealed she still suffers from depression after the attack that scarred her face.
“I live with anxiety and I still get depressed, because you don’t go through life-changing things and just get better and it’s over. You learn to live with it,” she told the Daily Star.
“When you have another child, you have no downtime. I did feel depressed and low.
"But your body is going through changes, physically and hormonally, so I just tried to check in on myself to make sure it wasn’t spiralling."
Katie – who has two children with her husband of three years, carpenter Richard Sutton – says a healthy diet helps her fight anxiety and gain confidence.
“What we put in our bodies can make us feel depressed or anxious and it’s the same for fitness. I think it all joins up in this big circle,” she said.
In February 2008, Katie started a relationship with David Lynch after the pair began messaging on Facebook.
But just two weeks into their romance, Katie started having doubts and he later attacked her in a London hotel room.
Katie then went back to her flat in Golders Green and two days later, Lynch demanded she go to a nearby internet cafe.
However, it was a trap and Lynch had arranged for accomplice Stefan Sylvestre to wait outside her flat and throw sulphuric acid into her face.
Katie was rushed to the Chelsea and Westminster Hospital for emergency treatment as the acid had severely burned her face and blinded her in her left eye.
She was put in an induced coma for 12 days and had to undergo skin graft procedures.
She also had to wear a plastic face mask for up to 23 hours a day and in total has had 40 operations to treat her burns.
Just a year after the attack, the model then launched the Katie Piper Foundation to campaign for more specialist help for burns victims.
The attack was caught on CCTV and shortly after Sylvestre, who threw the acid at Katie, was arrested.
Later Lynch was arrested and the pair were both handed life sentences.
In 2015, Sylvestre went up for parole but his plea to be released from jail was dismissed.