The protagonist of the story is an adopted girl on the verge of adolescence, with blonde hair that is "a close enough brand of German blonde" and a "smile that is starving" when she shows it. Her eyes, however, are brown. She is fostered by the Hubermanns after her biological father "abandons" their family, her brother dies, and her mother is forced to send her to a foster home due to her belief (communism), which is forbidden at the time. Liesel is the "book thief" referred to in the title. Liesel is fascinated by the power of words, as shown in the quotation, "I have hated the words and I have loved them." She steals books from snow, fire, and the mayor's wife.
Hans Hubermann (Papa)
Liesel's foster father and husband of Rosa, Hans is a former German soldier during World War I, accordion player, and painter. He develops a close and loving relationship with Liesel, and becomes a main source of strength and support for her throughout the novel. He, like Liesel, doesn't have much experience with reading. Together, the two help each other with reading and write all the words they learn on a wall in the basement with his cans of white paint. He helps Max because Max's father sacrificed himself to save Hans in World War One.
Rosa Hubermann (Mama)
Liesel's sharp-tongued, often abrasive, foster mother, she has a "wardrobe" build and a displeased face, brown-grey tightly-cinched hair often tied up in a bun, and "chlorinated" eyes. Despite her temper, she is a loving wife to Hans and mother to Liesel. To supplement the household income, she does washing and ironing for five of the wealthier households in Molching.
Liesel's neighbor, Rudy, has bony legs, blue eyes, lemon-colored hair and a penchant for getting in the middle of situations when he shouldn't. Despite having the appearance of an archetypal German, he does not directly support the Nazis. As a member of a relatively poor household with six children, Rudy is habitually hungry. He is known throughout the neighborhood because of the "Jesse Owens incident", in which he colored himself black with coal one night and ran one hundred meters at the local sports field. He is academically and athletically gifted, which attracts the attention of Nazi Party officials, leading to an attempted recruitment. His lack of support for the Nazi party becomes problematic as the story progresses. Rudy becomes Liesel's best friend, and eventually falls in love with her, always trying to get a kiss out of her...
A Jewish fist-fighter who takes refuge from the Nazi regime in the Hubermann's basement. He is the son of a WWI German soldier who fought alongside Hans Hubermann, and the two developed a close friendship during the war. He has brown, feather-like hair and swampy brown eyes. During the Nazi reign of terror, Hans agrees to shelter Max and hide him from the Nazi party. During his stay at the Hubermanns' house, Max befriends Liesel, because of their shared affinity for words. He writes two books for her and presents her with a sketchbook that contains his life story, which helps Liesel to develop as a writer and reader, which, in turn, saves her life from the bombs. 
The wife of the mayor of Molching who employs Rosa Hubermann. She entered depression after the death of her only son in the Great War. Ilsa allows Liesel to visit and read books in her personal library. She also gives Liesel a little black book, which leads Liesel to write her own story, "The Book Thief".
Liesel's little brother, who died suddenly on the train with his mother, while being transported to their foster parents.
Paula Meminger (Liesel's Mother)
Liesel's mother is only mentioned in the story a few times. Liesel's father was taken away by the Nazi's prior to the novel starting because he was a Communist, and the reason her mother – Paula Meminger – was taking both her children to foster care was to save them from Nazi persecution. Liesel's mother met the same fate as her father, but Liesel eventually realizes her mother gave her away to protect her.