The couple - who play Bella Swan and Edward Cullen in the Twilight Saga movie franchise - are believed to have rekindled their romance after Stewart had an affair with her Snow White and the Huntsman director Rupert Sanders.
However, it reportedly took a lot of effort by the actress to convince Pattinson to take her back.
The video apparently comprised photographs and footage of their life together, and made the actor realise he didn't want to throw their relationship away.
A friend of 22-year-old Stewart told The Sun: "She sent Robert the film after bombarding him with hundreds of texts, emails and answer phone messages.
"It was a last-ditch attempt at getting him back and she spent ages making the video montage using hundreds of photos and hours of home film footage of nights out and holidays."
It was speculated that Google Chrome's recent advert - which sees a man begging for his ex-girlfriend's forgiveness through a film - may have inspired Stewart's actions.
The source added: "It was just like the Google Chrome ad as she cut-and-pasted lines from love poems to connect it all together."
Photo gallery - Kristen Stewart and Robert Pattinson through the years: