
Three traits were added with World Adventures, six with Ambitions, one with Fast Lane Stuff, two with Late Night, two with Generations, four with Pets, three with Showtime, six with Supernatural, two with Seasons, three with University Life, two with Island Paradise, and two with Into the Future. They determine a Sim's behaviors, abilities, and their wishes, including their Lifetime Wishes. The traits also appear in The Sims Medieval this time, traits are adapted to the Medieval period.

Traits are the building blocks of a personality assigned to Sims in The Sims 3, replacing the previous system of personality points.

A Sim demonstrating the "Absent-Minded" trait For trait systems in other games, see Trait.
