A number of sources say a deal for seven-time world champion Hamilton to join Charles Leclerc at Maranello from 2025 has been agreed.
Ferrari and Mercedes have refused to comment.
Mercedes F1 staff were told in a meeting with team principal Toto Wolff and technical director James Allison on Thursday afternoon.
The move could be announced officially as early as Thursday evening.
Hamilton, 39, signed a new two-year deal with Mercedes only last summer. His contract is understood to have contained a break clause after one year, which Hamilton has chosen to exercise.
The possibility of Hamilton moving to Ferrari in 2025 was initially reported in the Italian and Spanish media on Thursday. BBC Sport has since confirmed the move through multiple sources.
There have been intermittent rumours of Hamilton moving to Ferrari for years. Until now, these have turned out to have little substance, but a number of sources say this is different.
The Hamilton deal has happened quickly. Ferrari were in negotiations over a contract extension with Carlos Sainz, whose deal runs out at the end of this season.
But Ferrari president John Elkann then discovered that Hamilton was a possibility and moved to secure his signature. The two are friends and have met each other socially on a number of occasions in recent years.
Hamilton won the most recent of his seven world titles in 2020 and signed his latest two-year Mercedes deal in August, which would extend his period with the team to 13 years.
Ferrari admitted to holding talks with then-reigning world champion Hamilton in 2019 about joining them in the future.
Red Bull have dominated the sport over the past two seasons since the controversial 2021 Abu Dhabi Grand Prix, when Hamilton lost out to Max Verstappen after former FIA race director Michael Masi ignored the rules in operating a late-race safety car period.
