Lina is a twelve-year-old girl who loves to run and desperately wants to work as a messenger for the city of Ember. She lives with her grandmother and baby sister in an apartment filled with mismatched furnishings. She frequently draws pictures of an imagined bright city, driven by a powerful intuition that a world exists beyond Ember's darkness. Her natural curiosity places her at the center of the city's deepest mysteries when she uncovers a damaged historical document.

Doon is a twelve-year-old boy who lives with his father above the Small Items shop. He is mechanically minded and studies the world closely, keeping a notebook on insect behavior. He trades his messenger assignment for a Pipeworks job to get closer to the city's failing generator, hoping to single-handedly save Ember from permanent blackouts. He struggles with frustration when he realizes the machinery is far beyond his understanding.

Mayor Cole is the current leader of Ember, described as a vast, heavy man with a grayish complexion. He publicly insists that the city's increasing blackouts and supply shortages are under control, urging citizens to remain calm and unquestioning. Behind his authoritative public persona, he dismisses anyone who challenges the status quo.

Clary is a tall, physically strong woman who manages Ember's agricultural greenhouses. She previously worked alongside Lina's deceased father and maintains a protective bond with Lina. She quietly observes the alarming disease affecting the city's potato crops but maintains a calm perspective, acting as a grounding force for the younger generation.

Mrs. Murdo is a neighbor to the Mayfleet family whose paper and pencil shop closed years ago due to city shortages. She maintains a highly organized approach to life, keeping her apartment exceptionally tidy. She actively steps in to help Lina's family, offering a safe haven when Granny's confusion creates household instability.

Granny is Lina and Poppy's grandmother and their primary guardian following the death of their parents. Her mind is beginning to slip, leading her to obsessively tear apart her closets looking for an important lost item. She vaguely remembers her grandfather insisting this missing object was critical for the city's future.

Poppy is Lina's baby sister. She requires constant care and supervision from Lina and their neighbors. As an active toddler with a habit of chewing on paper, she inadvertently damages a crucial historical document discovered in their home.

Lizzie is Lina's childhood friend and a recent graduate assigned to work in the Supply Depot. Her position gives her firsthand knowledge of the city's rapidly depleting storerooms. She frequently focuses on her own complaints and is easily distracted by the promise of rare luxuries.

Looper is a shopkeeper on Night Street who sells extremely rare items, such as colored pencils, at exorbitant prices. He also works shifts in the city's storerooms, granting him access to areas most citizens assume are completely empty.

Captain Fleery manages the messengers of Ember, overseeing the city's only method of long-distance communication. She is a strict but fair supervisor who stays physically fit to lead her team. She belongs to the Believers, a religious group convinced the original Builders will eventually return to rescue the citizens.

Doon's father manages a shop filled with bits and pieces of reclaimed materials, making a living by repurposing discarded items. He acts as a steady, grounding presence for his son, encouraging Doon to channel his anger into careful observation of the world.

Sadge is a citizen of Ember who attempts to leave the city by walking out into the unlit Unknown Regions. He quickly returns completely terrified by the sensory deprivation, serving as a public cautionary tale regarding the dangers outside Ember's borders.

Podd Morethwart served as the seventh mayor of Ember and is a distant ancestor of the Mayfleet family. Suffering from a fatal illness, he attempted to force open a locked, timed box entrusted to the mayors, hoping it contained a cure. His failure to pass the box to his successor created the city's current crisis of ignorance.

Arlin is Doon's immediate supervisor in the underground Pipeworks. She guides him through the dangerous, wet tunnels and insists he focus entirely on patching basic leaks rather than attempting to understand the massive, failing generator.

Dr. Tower is a medical practitioner in Ember. She struggles to provide effective care for her patients because the city's supply of useful medicine has been almost entirely depleted over the generations.