The stopper, 28, was heading to Birmingham to undergo his medical.
And if he passes, as expected, his signing will be announced by Villa imminently in a £20million deal.
The Argentinian has agreed a long-term contract believed to be worth around £60,000-a-week to join Dean Smith's team.
Martinez was a revelation between the sticks for the Gunners last season.
The stopper went on the star as the North Londoners won the FA Cup in August.
And he kept his place ahead of Leno for the recent penalty shoot-out victory over Liverpool.