Plummer plays John Paul Getty in the drama, after having replaced Kevin Spacey just weeks before the film’s scheduled release.
In a new interview, Scott has revealed that Plummer’s extensive work in theatre prepared him to learn so many lines in such a short space of time.
“Christopher does a lot of theatre, so he has a very good memory for remembering all those words,” he told HeyUGuys.
“Therefore, being a famous theatre actor as well it helped him remember [the script].
“It is challenging to remember all those lines in a short space of time but it helped he was a theatre actor.”
All The Money In The World also stars Mark Wahlberg and Michelle Williams, and has been generally well received by critics.
In another interview, Scott said the decision to replace disgraced Spacey was made quickly – and was as much of a commercial one as a moral one.
“I was completely taken by surprise, but honestly, within an hour, my commercial head starts to click in and I realised I had to do something about it immediately,” he said on BBC Radio 4.
“Christopher Plummer had always been there, almost alongside Kevin from the start as the possibility of Getty, so I went straight to Christopher.”
Plummer and Williams are in contention for Golden Globes this weekend.
All The Money In The World is out now in the UK.