The "after 7 years Allie and Noah" scenes were shot first and then the crew/cast went on a Christmas break. Ryan Gosling had to lose the beard and 20lbs he'd had as the older Noah and come back to play the young Noah. Rachel McAdams and Ryan Gosling were rather shy and unsure around each other in the "after 7 years" scenes but were more comfortable together in the young Allie and Noah scenes.
Rachel McAdams auditioned for the role during another movie's premiere. She was given the script just a day in advance. She beat nine other actresses for the role. The scenes used during her audition included the one of Allie's and Noah's argument at the end after Allie and her mother return from their morning drive.
Rachel McAdams and Ryan Gosling were both born in London, Ontario, Canada. Walt Whitman, quoted in the classroom scene ("Do I contradict myself?") and other parts of the movie, had a long friendship with 19th century London, Ontario, psychiatrist Dr. Maurice Bucke, which was depicted in the film Beautiful Dreamer (2006) .
The pictures of an older Allie and Noah through the years are actually the personal photos of Gena Rowlands of her and her husband and director Nick Cassavetes' father John Cassavetes with James Garner's face photoshopped in over John's face.