© BBCThe image resembled older known portraits of Leonardo
The drawing had been obscured by handwriting for 500 years before being discovered by Italian scientific journalist Piero Angela.
After months of restoration work, the image was aged using criminal investigation techniques and compared with older self-portraits of Leonardo.
The findings will be revealed on Italy's RAI television channel.
In a statement on RAI's website, Mr Angela said he initially discovered what looked like a nose underneath writing in Da Vinci's Codex on the Flight of Birds notebook.
Painstaking restoration work revealed an image of a young to middle-aged man with long hair and a light beard who appeared to be absorbed in thought.
Mr Angela said he compared the image with known later self-portraits of Da Vinci and consulted facial surgeons and police forensic experts - all of whom agreed there were strong similarities.
Professor Carlo Pedretti, a world authority on Da Vinci studies who worked on the project, said he was "perfectly convinced" that the image was of the artist.
If confirmed, he said, the image would be of great importance to the study of Da Vinci's work and thoughts.
This is indeed a very early portrait of the great artist Da Vinci who is an inspiration for every artist even today. I have started learning art from some time and would love to make a mark like this great artist. For the time being, you can check my work at [Link] online.