One major change to Create a Sim functionality is that sliders have been replaced by direct mouse manipulation. By clicking, dragging, and pulling with the mouse, players may directly manipulate the facial features of a Sim. Players can directly manipulate any body part including the abdomen, chest, legs, arms and feet. In previous Sims games, only the fitness and fatness can be manipulated on a Sim's body; however, fitness and fatness levels may still be adjusted in The Sims 4 with sliders as in previous games. The base game comes with over 40 hairstyles for both male and female Sims. There are up to 18 hair color options per hairstyle. Selections of premade designs of Sims are available to choose from, and range in body shape and ethnicity.

Seven life stages are available including baby, toddler, child, teenager, young adult, adult and elder. The baby life stage is accessible only through the birth of a Sim and not available in Create a Sim. Toddlers were initially absent from the original game release, but were added in the January 2017 patch.[9][10]

Each Sim has three personality traits and an aspiration containing its own hidden trait.

Compared to previous Sims games where everyday, formal, sleepwear, athletic, party and swimwear outfits were restricted to having their own clothing options, all clothing options are available across all outfits and players are allowed up to 5 outfits per category. There is a filter panel where clothing options can be sorted by color, material, outfit category, fashion choice, style, content and packs.

In a summer 2016 update, gender options were expanded in the game, allowing any gender expression. With this update, haircuts and outfits can be worn by any Sim of any gender, and pregnancy can become a possibility regardless of the gender