Rosalind Penderwick - A caring, responsible 12-year-old, Rosalind, as the eldest sibling, has looked after the family since her beloved mother died four years prior. Rosalind, in more than one way, acts as the parent-like sibling to all of her sisters (particularly to Batty) and usually is the voice of reason among the sisters. However, throughout the first book, she tries to figure out her true feelings for Cagney, the gardener at Arundel Hall. Rosalind is prone to worrying and misses Mrs. Penderwick a lot. Her sisters say that she still cries in her sleep sometimes. She often is the one who calls the MOOPS (Meeting of Older Penderwick Sisters) and the MOPS (Meeting of Penderwick Sisters). She enjoys baking, and speaking on the phone with her best friend, Anna, and is also quite skilled at basketball. She begins dating her neighbor Tommy Geiger several months after her thirteenth birthday in April.
Skye Penderwick- A tempered, energetic, and witty 11-year-old, Skye is vastly different from her sisters, most notably in appearance. With straight blonde hair and blue eyes, Skye resembles her mother (her other sisters have brown curly hair and brown eyes), but does not consider herself able to match her mother's beauty. Being the most outrageous and tomboyish of the group, Skye is often at odds with her sisters for their more "feminine" likes. Skye plays soccer and enjoys playing the sport with her sister Jane and her friend Jeffery which the Penderwicks meet in the first book. She is most awkward with Batty, for Skye is not much with babies and kids. Skye often seeks Rosalind's advice on matters such as temper and feelings, and is excellent at math (she knew long division by second grade, and is excused from her sixth-grade math class so she could teach herself geometry in the library). She is also described as being an abominable musician, with her clarinet lessons having been canceled when a neighbor complained. She plans to become an astrophysicist as a career, and during her trip to Point Mouette brought her favorite book Death by Black Holes.
Jane Penderwick - A dreamy and artistic 10-year-old who works to be a famous and respected author, Jane has already begun writing a series of short books, following a heroine Sabrina Starr as she rescues various animals, and later people. Jane often confuses life with fantasy, getting lost in her fanciful imagination which sometimes bothers Skye. In addition to Sabrina Starr, Jane possesses an alter ego, Mick Hart, a rough-mouthed British character who keeps her from crying during soccer games. She and Skye are the closest of the four sisters, although they often rub each other the wrong way because of their vastly different personalities (exemplified by their room at home, in which Skye's half is kept tidy and white while Jane's is painted lavender and perpetually cluttered). Her writing style often incorporates items from past literature and legends, and she supposedly hates revising, choosing instead to maintain her original ideas. Her writing process is followed throughout the series, as she completes a Sabrina Starr book in each Penderwicks novel; she also writes a play, "Sisters and Sacrifice", which, though written while switching homework assignments with Skye, is chosen as the sixth-grade play.
Elizabeth Penderwick (Called Batty) - The youngest child, Batty is a very innocent and very shy 4-year-old who is a great lover of animals and her family. Batty always asks Rosalind to tell her a story about their mother every night at bedtime. She is very fond of Hound, the family dog, as he is of her, and is also fond of Cagney's rabbits, Yaz and Carla, and visits them almost every day to give them carrots. She almost always hides behind her sisters when she meets a new person and, for the first book, always wore orange-and-black dress-up butterfly wings, for an unknown reason. During the second book, she befriends Ben, the toddler who had recently moved next door, often spying on "Bug Man" with him. During her summer at Point Mouette, she is taught music by Jeffrey and proves to be a very able musician.
Jeffrey Tifton - An only child who turns 11 during the first book, Jeffrey led a largely contented, if dull, life before meeting the Penderwicks, as he lived in a grand estate called Arundle Hall with a kind housekeeper, Churchie, to care for him. His father had left him before he was born, and Jeffrey initially does not know anything about him. Jeffrey had suffered the loss of his grandfather, a well-known general, at age seven, and his mother had designed for Jeffrey to follow in his footsteps, attending Pencey Military Academy and then West Point. However, Jeffrey, is an immensely talented musician, who plays piano, clarinet and a little cello. He wants to be a musician, and vehemently protests this fate. With the aid of the Penderwicks, he manages to tell her his opinions, and eventually enrolls at the Welborn-Hughes boarding school in Boston while taking private lessons at the New England Conservatory. His musical ability is later revealed to come from his father, whom he meets at Point Mouette. His birthday is August 8.
Ben Penderwick -Iantha's son and the Penderwicks step-brother
Lydia Penderwick - the youngest Penderwick (as of book 4). The Daughter of Mr. Penderwick and Iantha and the Penderwick sisters' half sister. Not much is known about her character because she is only 2 years old in the fourth book, but it is rumored that she is the central character in book five
Martin Penderwick - The head of the Penderwick household, he is a very loving and caring, if often absentminded, and always forgets where his glasses are. A professor of botany at Cameron University, he frequently uses Latin in everyday speech, and also enjoys classical music, particularly opera. Following the loss of his first wife, Elizabeth, he is able to look after his four daughters well, yet he feels guilty that his eldest daughter Rosalind had taken over many of her mother's duties, being the one to advise and comfort her sisters. He marries next-door neighbor and colleague Iantha Aaronson in the second book.The Penderwicks at Gardam Street. He is largely absent from the third book.
Elizabeth Penderwick - The mother of the sisters, she died from cancer shortly after Batty's birth, and thus is not present in any of the series. The only time she appears in the books (except for some occasional mentions made by the sisters) is in the prologue of ‘'The Penderwicks on Gardam Street.' With blond hair and blue eyes (like her daughter Skye), she is regarded by all the sisters to be beautiful. Shortly before her death, she writes a letter detailing her worries that Mr. Penderwick would be lonely after her death, and advises him to resume dating. This letter is delivered by Mr. Penderwick's sister Claire four years later, setting the second book's events in motion.
Claire Penderwick - Mr. Penderwick's younger sister, she first made an appearance in The Penderwicks on Gardam Street, bringing a letter from the sisters' late mother that advised Martin resume dating. She takes great pains to find suitable matches for him. The following summer, she supervises the sisters at Point Mouette, yet she injures her ankle at the seawall and is subsequently on crutches. She is single, although she had numerous relationships in college, and spends much time at Point Mouette solving jigsaw puzzles with Turron. She lives in Connecticut, several hours away from the sisters' home at Cameron, but visits often.
Iantha Aaronson Penderwick - Having lost her first husband, Dan, in a car accident, she and her son Ben move into the house next to the Penderwicks'; interestingly, she and Ben are the only people on Gardam Street with red hair. She is naturally shy, yet she gets to know the four sisters well, especially Batty, whose company Ben greatly enjoys. She is a professor of astrophysics at Cameron University, a profession which Skye greatly admires. For a brief period, an ex-colleague of hers, Norman, attempted to steal her research. After a while, she gets to know Mr. Penderwick better, and they start to date. Then they get married. It turns out that the whole dating idea that Mrs. Penderwick had, wasn't such a bad idea, and wasn't as torturous as Mr. Penderwick said it was, because not long after, Iantha and Mr. Penderwick get married.
Brenda Tifton - The mother of Jeffrey who is rude, cruel, and snobby toward the Penderwicks. Mrs. Tifton believes the Penderwick sisters to be vulgar (which she evaluated after Jeffrey's birthday dinner), and dislikes all of the sisters, although Jane seems to escape her criticism no she doesn't. During the first book, she is obsessed with winning a garden competition, in which she eventually takes second place after Jeffrey and the sisters destroy a jasmine plant with a soccer ball. She marries Dexter Dupree, an equally snobby man, following the first book, and embarks on a worldwide honeymoon. She permits Jeffrey, at the last minute, to join the sisters at Point Mouette.
Alec McGrath - the Penderwicks' next door neighbor at Point Mouette, he earns Jeffrey's admiration because of his comprehensive music room (containing many instruments, including a grand piano). He also owns a dog, Hoover, who creates many problems for the Penderwicks, and primarily lives in Boston. After shaving his beard, it becomes apparent to Skye and Jane the similarity between him and Jeffrey, and eventually it is revealed that he is Jeffrey's long-lost father, a fact Jeffrey has extreme trouble with.
Dexter Dupree - A publisher for a car magazine, "Lines on the Road". He also enjoys golfing, and has a prominent smirk (which makes its way onto Skye, Jane, and Jeffrey's archery target). These three children also name one of their soccer balls Dexter so they could kick him around (the other ball being named "Pencey Military Academy"). He marries Mrs. Tifton, and, in the third book, arrives at Point Mouette to try to take Jeffrey home.
Mrs. Churchill ("Churchie") - The caring housekeeper at Arundel who "makes the best gingerbread in Massachusetts", she is described by the sisters as being "cozy". She helped the girls pick out suitable outfits from Mrs. Tifton's closet for Jeffrey's fancy birthday dinner (as Mrs. Tifton had too many dresses to keep track of). She has a daughter in Boston, as well as (presumably) several grandsons; as a result of her lack of granddaughters, she enjoys altering the sisters' party dresses to fit.
Cagney - the gardener for Arundel Hall. He enjoys playing basketball and reading about the Civil War. His favorite snack is chocolate brownies, and he owns two rabbits, Yaz and Carla. He is, according to Rosalind, very handsome. Rosalind initially estimates his age at "eighteen, maybe nineteen years old". He dates a girl named Kathleen, although they break up before the end of the first book. He begins teacher-training lessons several months after the Penderwicks' summer at Arundel. Jeanne Birdsall's dog, Cagney is named after him, not the other way around.
Harry "the Tomato Man" - an old man who sells tomatoes and is good friends with Churchie. He helps the Penderwicks find Arundel.
Turron Asabere - a close friend of Alec, he visits Point Mouette from his regular home in New York and saves Jane, who had fallen down a rock by the sea and thought she had broken her nose. He is "terrified" by boats (to use his term) and spends much of his time at Point Mouette completing jigsaw puzzles with the injured Aunt Claire.
Anna - Rosalind's best friend, with whom she shares all of her middle school classes. Anna is not directly in the first book, but Rosalind often makes references to her copious and strongly-opinionated advice, especially about Cagney. Her father had divorced and remarried countless times, to the extent that Anna resolves to call of her stepmothers "Claudia" (after the first one). She also spends much time with her mother. She plays a considerable role in arranging blind dates for Mr. Penderwick during the second book. She takes Rosalind on a vacation to New Jersey the following summer, resulting in both being absent from the third book.
Tommy Geiger - a neighbor of the Penderwicks (he lives across the street from them), he is twelve as of his first appearance, and is thus in Rosalind's grade. He is an avid football player, wearing Cameron Middle School number 86, and works out in his spare time. He had played the starring role in his sixth grade performance (Dr Jekyll and Mr Hyde) and also had worn mismatching socks to his graduation, and also eats a large amount (although Rosalind describes him as being "too skinny"). He plans on being a pilot when he grows up. His affection for Rosalind becomes apparent at the beginning of The Penderwicks at Gardam Street, but her indifference leads him to date an eighth-grade cheerleader, Trilby Ramirez, for several weeks, during which he and Rosalind have an argument and then ignore each other. However, the two make amends and, Tommy having left Trilby, begin dating after Rosalind's thirteenth birthday in April.
Mr. Geballe - Skye's sixth grade teacher, he is in charge of the sixth grade play, and so it is he who selected Jane's play (masked as Skye's) to be the play for the year, and casts Skye for the lead part despite her hatred of acting. He is kind and trusting, as demonstrated by his complete lack of suspicion, even though he knows Skye to dislike creative assignments.
Miss Bunda - Jane's fifth grade teacher, she frequently assigns essays to her students on topics like "Famous Women in Massachusetts History" and "How Science Has Changed Our Lives". Jane, preferring creative writing over essays, receives a "C" on her "Women in Massachusetts" essay because she wrote about Sabrina Starr. Similarly to Mr. Geballe, she is completely deceived by Skye and Jane's homework switch. Miss Bunda is described as boring by Jane.