The stars worked together on 2011 movie Mission: Impossible - Ghost Protocol.
While Simon has remained relatively under the radar, Tom is a huge Hollywood star and often appears in gossip columns.
His split from ex-wife Katie Holmes was well documented and Simon thinks his colleague leads a bizarre existence.
'His life is crazy, but he's built himself for the very purpose of making films. That's who he is,' Simon mused to Total Film.
'When working with him, I met someone who I found to be extremely good company with an incredible work ethic. Nothing ever came up about all the weirdness you see written about him. Just didn't.'
Having started off in smaller flicks, Simon has now made a name for himself and features as Montgomery 'Scotty' Scott in the Star Trek movie franchise.
However, the 43-year-old remains down to earth.
'I live in Hertfordshire. People kinda assume things about film actors that are kinda wild...' he said.
'Yeah, Tom Cruise emails me occasionally. But because I've worked with him, he's been demythologised. It's not particularly weird if he emails me, because we're kinda colleagues, in a weird way. But I still get quite excited if I get an email from him. I tell Maureen, my wife, 'Tom Cruise is emailing!''
Star Trek Into Darkness also stars Chris Pine and Benedict Cumberbatch and is in cinemas now.