Jamie Hutcheon, 25, founded Cocoa Ooze in 2008 and now employs more than 20 staff.
He sought £70,000 for a 10% share of his business, and four of the Dragons turned him down.
But retailer Touker Suleyman offered it for 35%, which he agreed to reduce to 20% once he has his money back.
Mr Hutcheon's aim is to use the money for a new production unit.
He said: "It's a fantastic opportunity. I am a self-taught entrepreneur. I am 100% passionate about it."
He was 17 when he started the business in the family kitchen. The business now features a retail shop and coffee shop, as well as running parties for children.
He was described on the programme as Aberdeen's wannabe Willy Wonka, from Roald Dahl's children's novel Charlie and the Chocolate Factory.
Mr Suleyman told him: "I think you are the business. I am going to make you an offer.
"I look forward to working with you - and eating lots of chocolate."
Mr Hutcheon said afterwards: "Getting that offer was a sigh of relief.
"I came here with nothing, I go away with a well-connected Dragon."
A man who founded an Aberdeen chocolate business has landed a £70,000 investment on the BBC Two Dragons' Den television show.