The Oscar-winning stars fuelled ongoing speculation about a possible romance when they were spotted making a coffee run on Saturday. While Charlize, 38, picked up the drinks, Sean, 53, waited for her in the car.
"They were both smiling," a witness told People, adding that Sean seemed "very happy and relaxed.
After returning to Charlize's house, the couple emerged the following day for a trip to the cinema, catching Leonardo DiCaprio's new film, The Wolf of Wall Street, on Sunday night at the ArcLight Hollywood.
Charlize and Sean have been virtually inseparable since they were spotted last week in Hawaii, where the Gangster Squad star has a house.
Reps haven't yet commented on their relationship.
South African beauty Charlize, who is a mum to two-year-old Jackson, has been single since splitting from her longterm boyfriend Stuart Townsend in 2010.
Twice-divorced Sean, famously married to Madonna in the 80s and Robin Wright in the 90s, has previously been linked to Petra Nemcova and Scarlett Johansson.