"He is always checking up on her and making sure she is happy."
The story added the pair had been "inseparable" while filming the faith-based Sony Pictures' production movie, in which Garner plays the mother of a Texan girl who has been "healed" by God.
Another article headed Is Jennifer Garner Moving on From Ben Affleck With Her Miracles From Heaven Co-Star?, published by starpulse.com claims: "Martin is so warm and complimentary without crossing the line. Jen's in a good head space. As her friends joke, after all these years, Jen is getting her groove back."
OK! magazine also said the chemistry between Garner and Henderson was strong.
"Her flirtation and growing bond with Martin is just the thing to distract her."
But it added that Garner - who has three children with Affleck - wasn't yet ready to jump back into the dating scene properly.
Henderson's Los Angeles-based agent Martin Cooper did not respond to an interview request.
The former Shortland Street star, who has replaced Patrick Dempsey's McDreamy as the new resident heart-throb on US smash hit Grey's Anatomy, is no stranger to dating beautiful women.
He has been been linked to screen queens Marnette Patterson, Radha Mitchell and Aishwarya Rai Bachchan.
In 2012, he had a brief relationship with GI Jane star Demi Moore after her split from ex-husband Ashton Kutcher.
Garner has been embroiled in a messy break-up with Affleck.
He has been accused of dating their children's nanny Christine Ouzounian, which the double Academy Award-winning actor has denied.
