The West Wing star has been in the UK to promote his new film The Way, which is set for release on April 15.
His son Charlie, star of Two and a Half Men, is currently undergoing rehab treatment at his home in LA and his actor father spoke out about his son's problems.
Speaking to Sky News, Martin, 70, said: 'He's an extraordinary man, He's doing well.
'We pray for him. If he had cancer how would you treat him? This disease of addiction is a form of cancer.
'You have to have an equal measure of concern and love.'
He remains philosophical about his son's ongoing struggles.
'You realise we're not all on the same journey all the time,' he said.
'We have to love that much more. We have to be that much more present.'
