Everton have made speedy progress in talks with the Gunners to get a deal towards the line, with the finer points of the agreement being hammered out for the England forward who started his medical during the afternoon.
Arsenal are set to receive an initial fee of £20m for Walcott, with the rest in performance related add-ons.
The move will bring to an end his 12-year stay at Arsenal, during which he scored 108 goals in 397 appearances.
But Walcott is keen to kick-start his career at Goodison Park after falling out of favour at the Emirates Stadium.
He has not started a Premier League match this season, and accepted he had to leave after Arsenal manager Arsene Wenger admitted that he could not offer the forward regular game time.
Everton manager Sam Allardyce has been desperate to boost the attacking options of a squad blunted by the failure to sign an adequate replacement for last season’s top scorer Romelu Lukaku.