The 28-year-old star - who has a huge following on social media - has revealed he made an eye-watering profit on his initial investment, but its value has already evaporated following the recent fall in the value of Bitcoin.
He told the 'Private Parts' podcast: "I put £2 million into Bitcoin – well, I say Bitcoin. I put [in] £2 million last year – November, December – but this was into cryptocurrencies.
"I made £7 million and now I’ve lost it all. It’s mental. It’s been a full journey, but I had to experience it. I fully understand it now. I put money in things where I essentially leveraged myself and I kinda over-leveraged myself to a point where I lost money because of it."
KSI explained that the situation was triggered by the "Bitcoin crash".
Despite this, the YouTuber - who has also enjoyed success as a rapper and as a professional boxer - has remained philosophical about the situation.
Reflecting on the crash, he added: "There’s no point crying over spilt milk."
And in spite of the dramatic crash, KSI thinks Bitcoin remains "the future".