Frank Lampard finalised his contract with Chelsea late on Wednesday night after holding over six hours of talks at Stamford Bridge.
Chelsea are expected to announce Lampard's appointment on Thursday.
Derby County granted Chelsea permission to speak to Lampard last week and the 41-year-old was at Stamford Bridge until 1.32am on Thursday morning to finalise the terms of his deal to succeed Maurizio Sarri.
It is believed Lampard has been seeking assurances about owner Roman Abramovich's expectations and the club's plans once FIFA's transfer embargo expires.
Sky Sports News have been told the interview process included an open exchange of views, with both sides wanting to be certain the relationship would work for them.
Lampard won 11 major trophies, including three Premier League titles and the 2012 Champions League during his 13 years at Chelsea.
The former England international also remains the club's all-time leading scorer with 211 goals.