Bojack Horseman

A self-loathing cynical alcoholic horse currently in his 50s, whose acting career peaked when he starred in a successful 1990s family sitcom called Horsin' Around. Though he began as a young bright-eyed actor, he has since grown bitter, deeply depressed, and jaded towards Hollywoo and who he has become post-fame. BoJack has been shown to be caring and insightful, but his insecurities, loneliness, desperate need for approval, and guilt over his own actions often result in self-destructive and selfish actions which devastate those around him. His past and present relationships with his abusive alcoholic parents and his attempts at overcoming their legacy are a continual theme of the series.

Princess Carolyn

A pink Persian cat who is BoJack's agent in the first three seasons and former on-and-off girlfriend. Hailing from Eden, North Carolina, the earnest and unflagging Princess Carolyn was a top agent at Vigor agency through her tireless pursuit of new talent and large network of odd personal connections. Though she struggles to find a balance between work, her troubled personal life, and taking care of BoJack and her friends, she enjoys her fast-paced hectic lifestyle. She left Vigor to start a new agency with her then-boyfriend and coworker Rutabaga Rabitowitz. After recognizing his lack of trustworthiness and confronting her fear of being alone, she ultimately decides to leave him and run the new company named VIM by herself. After several setbacks, Princess Carolyn closes VIM in season 3, only to reopen it as a management agency. She struggles throughout the series in starting a family and suffers several miscarriages. In season 5, after several failed attempts, she successfully adopts a baby porcupine from Sadie, a young woman from her hometown. In the series finale, she marries Judah, her loyal assistant.

Diane Nguyen

A human ghostwriter, a well-schooled, misunderstood intellectual, and a Vietnamese-American third-wave feminist from Boston. She is a thinker who wants to make the world a better place for women and wants others to behave according to her morals even though she often breaks them. While writing BoJack's memoir, Diane and BoJack develop a strong friendship that initially becomes awkward and strained after BoJack develops romantic feelings for her, especially as she was dating Mr. Peanutbutter at the time. She eventually marries Mr. Peanutbutter, but during and after Mr. Peanutbutter's run for Governor of California, their marriage begins to deteriorate, and they divorce at the beginning of season 5. She eventually realizes she has depression, and gains weight as her mental health improves due to antidepressants; news media celebrated the series' realistic portrayal of her changing body shape as a sign of improved health.[14] During the sixth season, Diane develops a relationship with a buffalo named Guy (whom she goes on to wed) and comes to terms with her neglectful upbringing. She is a graduate of Boston University.

Mr. Peanutbutter

An energetic, optimistic and cheerful yellow Labrador Retriever who is BoJack's former sitcom rival. Mr. Peanutbutter was the star of Mr. Peanutbutter's House, which, according to BoJack, "borrowed the premise" from Horsin' Around. Despite their rivalry, Mr. Peanutbutter cares a great deal about BoJack's opinion and admires him for his work on Horsin' Around. He has an especially good relationship with Todd, and his positive attitude and financial resources combined with Todd's outlandish schemes and plans often result in the two starting questionable business ventures. Mr. Peanutbutter has been married three times (to Katrina Peanutbutter, Jessica Biel and Diane Nguyen). In "Old Acquaintance", it is revealed that "Mr." is his actual first name. He is a graduate of Northwestern University and a native of Newfoundland and Labrador, Canada. His character was initially created as a foil for BoJack, but then evolves into an important character himself.

Todd Chavez

An unemployed, silly but vastly talented 24-year-old human slacker who ended up at BoJack's house for a party five years before the beginning of the series and never left. Although BoJack constantly voices disdain for him, his actions speak otherwise and he genuinely cares about Todd, continuing to unconditionally support him financially and sabotaging his attempts to gain independence. Todd has been shown to possess a plethora of skills including an understanding of Japanese, entrepreneurial know-how—allying with Mr. Peanutbutter for various business ideas—and writing and composing his own rock opera, which was eventually sabotaged by BoJack. This and other examples of BoJack's poor behavior towards him lead Todd to break ties with BoJack in season 4. Todd also has an uncanny knack for getting himself in absurd and extremely dangerous situations when his friends aren't around, such as getting into gun fights on several occasions, ending up in prison, and in one case, switching places Prince and the Pauper–style with a Cordovian dictator. He is also almost never seen without wearing his signature yellow beanie and red hoodie. In his teenage years, he was an aimless skateboarder, and the object of affection of his schoolmate Emily. He realizes in the season 3 finale "That Went Well" that he is asexual. In season 6, Todd forms a relationship with a rabbit named Maude who is also asexual.