Eden is noted to be a very warm individual, despite all the years she spent serving the Volturi and feasting upon human blood. She is said to be stubborn and strong willed at times. She has a very bright personality, and is constantly commented to have a very warm aura about her - something that helps attracts spiritual beings to her so she can help them. Eden puts her free time to use since vampires do not sleep. She employs the night hours reading books, playing video games with her adoptive brother Emmett, or trying out the latest fashion/make-up with her adoptive sister, Alice. Eden enjoys listening to a wide range of music, stating that she enjoys listening to anything that catches her mood. However, she enjoys making jokes about her brother's choice in music. 


"I felt my jaw drop in astonishment as my eyes met hers. Every feature the woman had was Edward's - her eyes, her lips, her bronze hair - everything she possessed was Edward's. They could have been twins for all I knew. I motioned my gaze towards Edward and saw that he was staring at her with shock and confusion. He knew her. Only one word escaped his lips. "Eden?"
—Bella in New Moon after seeing Eden for the very first time.
Eden is noted to be the splitting image of her brother, Edward, as the two of them are often mistaken for being twins. She is described by Bella as being extremely beautiful, just like all vampires. Her skin is as hard as marble, very pale and ice cold. Her skin, like all vampires, sparkles as though a thousand diamonds are embedded into her skin when in contact with sunlight. Her facial features are said to be perfect - high cheekbones, straight nose and full lips. Eden has long wavy bronze hair that she inherited from her mother, Elizabeth Masen, as well as Edward. Her eyes, once an emerald green, are now a crimson red. However since joining the Cullen family and adapting to their animal diet, her eyes eventually turned into a golden brown colour. Her appearance changes if she goes long without feeding; her eyes darken, becoming onyx black and purple bruise-like shadows appear beneath her eyes. She is remaining frozen physically at 17, though she is technically over a hundred. 

When Renesmee (Eden's niece) is born, she is repeatedly commented to look very similar, if not, exactly like her aunt Eden. In "The Short Second Life of Bree Tanner", Eden is referred to as the twin of the red-headed mindreader by Bree Tanner. When Eden returns to Forks, she and Edward pose as twins because of their similar age and striking resemblance.