Katherine is described as Elena's doppelgänger; this is observed by almost every character in the show and evenElena herself. Katherine is very beautiful and seductive. She has an oval face with beautiful facial features and structure.

She has long brown hair like Elena, although she prefers to wear her hair in curls, while Elena wears her hair straight, though Katherine will occasionally straighten her hair if she is trying to impersonate Elena, like she did for the Masquerade Ball. Katherine has almond-shaped, deep brown eyes with thick dark lashes, similar to 

Elena's eyes, although Katherine's eyes seem to be darker in color, and having a "smokey" and "shadowy" appearance. Katherine also wears heavier make up while Elena's is more casual. Katherine's overall appearance is described as sexy and seductive, while Elena's overall appearance is sweet, casual and sporty.

Katherine's sense of fashion is more chic and mature than Elena's. She seems to favor clothes which are black in color and is often seen wearing tight leather pants and spike heels. Elena, on the other hand, favors jeans and T-shirts and frequently wears Converse sneakers. There is a cool and elegant demeanor about Katherine. Katherine always wears a blue lapis lazuli necklace, made by Emily Bennett, to protect her from the sun while Elena wears a vervain necklace, given to her by Stefan, to protect her from being compelled by vampires. Katherine is very vain and narcissistic about her looks, and has no problem using her sexuality and her beauty to get what she wants. Stefan said that Katherine does not care about others; she only cares about herself, although Katherine has repeatedly stated that she genuinely loves Stefan.