The winger was at the Merseyside club's Finch Farm training ground on Tuesday to undergo a medical and thrash out personal terms after a £20m fee was agreed with Arsenal.
talkSPORT understands the deal has now been finalised and Everton will announce the 28-year-old's signing on Wednesday morning.
Walcott was deemed surplus to requirements at Arsenal after 12 years in north London.
He has scored 108 goals in 397 matches for the Gunners but his last Premier League start for the the club came in April 2017.
The 47-cap England international becomes Everton manager Sam Allardyce's second signing of the transfer window.