The scene set in the church where Laura lights a candle for Christine was mostly improvised. Originally intended to show the gulf between John's and Laura's mental states-John's denial and Laura's inability to let go-the script included two pages of dialogue to illustrate John's unease at Laura's marked display of grief. After a break in filming to allow the crew to set up the equipment, Donald Sutherland returned to the set and commented that he did not like the church, to which Julie Christie retorted that he was being "silly," and the church was "beautiful." Nicolas Roeg felt that the exchange was more true to life in terms of what the characters would actually say to each other, and that the scripted version was "overwritten," so opted to ditch the scripted dialogue and included the real-life exchange instead.
Renato Scarpa, who plays Inspector Longhi, didn't speak any English: he just read the lines he'd been given without knowing what they meant. This added to the sinister quality of his character.
Shooting the drowning sequence was particularly problematic: Sharon Williams, who played Christine, became hysterical when submersed in the pond, despite the rehearsals at the swimming pool going well. A farmer on the neighbouring land volunteered his daughter who was an accomplished swimmer, but who refused to be submersed when it came to filming. In the end, the scene was filmed in a water tank using three girls.
Donald Sutherland and Julie Christie met for the first time on the set of this film. The first scene they had to shoot was the sex scene, as Nicolas Roeg wanted to "get it out of the way" and then move on to the "bone" of the matter. Christie was terrified.
The famous sex scene was completely removed by the Irish censor when 'Don't Look Now' was theatrically released in Ireland.