The actor, who plays Ian Beale, married dancer Beverley at Walt Disney World Resort in Florida back in 1998.
It is believed that EastEnders star Adam made the decision to end the relationship, but there is thought to be no third party involved.
A friend of the The 52 year old actor said: "Beverley was naturally very upset, as anybody would be in the circumstances, but these things happen and it's a straightforward separation.
Nobody plans for these things and divorce is a difficult thing to get your head around but they have dealt with it quietly for several months and are now telling friends so it's less of a secret.
"They still get on well, and are keen to make sure they stay that way for the sake of their children – even though they are now grown up," the pal continued to tell The Sun Online.
A spokesperson for the BBC soap confirmed the news, saying in a statement: "Beverley and Adam separated in August 2019 and we ask that the family's privacy is respected."
The couple have two children together, 27-year-old Jessica and 23-year-old Samuel.
The news of their separation comes after it was reported Adam would be stepping away from the soap for an "extended break."
While the reason for the character's break has not been revealed, it is expected to be related to Ian’s involvement in the death of Dennis – the son of Sharon (Letitia Dean).
EastEnders is off air until 7 September after filming was suspended due to coronavirus.
Adam, who is EastEnders' longest-running cast member, having played Ian Beale since 1985, is set to be at the centre of an “explosive twist” that will lead to him not appearing on-screen for up to 10 weeks.
An insider said: "Writers are staying tight-lipped about what happens, so it's not known yet what the future will hold for the character. There are no guarantees and anything can happen in Albert Square.
As the longest serving actor on the soap, having appeared in the very first episode back in 1985, fresh out of Sylvia Young Theatre School, it's believed Adam now earns between £200k-£249k per year.
Alongside Danny Dyer, Adam is one of the highest paid soap stars on the BBC, and has a varied mix of storylines and drama over the years in Walford.