Sam Dempster, 27, collapsed during a run in London’s Hyde Park on April 27.
He claims The Rain Man star, who has a house in the capital, was taking a walk and saw him collapse.
The actor then waited with the stricken lawyer until paramedics carried out resuscitation and rushed him to hospital.
Writing on his recovery blog “Heart-throbbing”, Dempster applauded Hoffman and the paramedics.
He said: “A big thank you also to my new found favourite celebrity Dustin Hoffman who called 999 and waited by my side until paramedics arrived and the staff at the Chelsea and Westminster Hospital that stabilised me before I was transferred to the Royal Brompton Hospital.”
The paramedics told The Sun newspaper the Oscar winner seemed “fascinated’ by what they were doing and that when they carried Dempster to the ambulance, he told them: “Great job, guys.”