Seasons 1–2

In season 1, he receives an advance to write a memoir, but after difficulties starting, his publisher hires Diane Nguyen as his ghostwriter.^[6] Despite difficulty during the writing process, the book receives positive reviews, and brings BoJack back into the spotlight. At one point, BoJack attempts to apologize to his old friend, Herb Kazzaz, with whom he originally created Horsin' Around. BoJack feels guilt over the fact that he did not defend Herb after Herb was fired in the 90s after being outed as gay. But, because BoJack took such a long time to make an effort, Herb rejects his apology. This event deeply affects BoJack for the remaining seasons.

In season 2, he lands the role of Secretariat in a biopic of the famous horse. However, he struggles with the role and with the production in jeopardy, he inadvertently causes Secretariat's director, Kelsey Jannings, to be fired. Overwhelmed, he escapes his troubles to New Mexico where he reconnects with his old friend Charlotte, who now has a husband, Kyle, and two kids, Penny and Trip. Unwilling to return to LA, he stays with Charlotte's family and becomes very close to them, especially Penny, and accompanies her and her friends Maddy and Pete to her prom where he gets them all drunk. As a result, Maddy gets alcohol poisoning, and BoJack threatens Pete into staying silent out of fear that the event could negatively impact BoJack's career. Later, Penny makes a pass at BoJack and he rejects her; however, when he and Charlotte kiss and she asks him to leave, Charlotte then discovers BoJack in bed with Penny. Charlotte threatens BoJack to leave and never contact them again and he reluctantly returns to Los Angeles where he discovers the new director finished shooting Secretariat and used a CGI version of BoJack instead.^[7][8] The movie is a critical and commercial hit upon its release.

Seasons 3–5

In season 3, Bojack's role in Secretariat earns him an Oscar nomination, though it is later revealed to be a mistake. Subsequently, he and his roommate, Todd Chavez, have a falling out. BoJack then copes by going on a drug-induced bender with his friend and former co-star in Horsin' Around, Sarah Lynn, which results in her death. Despite being hired again to do a sequel show to Horsin' Around, BoJack runs away fearing he will corrupt his female child co-star like Sarah Lynn and nearly attempts vehicular suicide, but stops upon seeing a group of cross-country running horses.

In season 4, he comes to terms with Sarah Lynn's death after months of avoiding the public eye at his old grandparents' summer house in Michigan and meets with Hollyhock, a young horse who at first believes BoJack to be her biological father, but is later revealed to be his half-sister as a result of an affair between BoJack's father and his maid. He also deals with his mother suffering from dementia. His mother lives with him after getting kicked out of her nursing home for a while until BoJack put her in a nursing home when he discovered she was spiking Hollyhock's drinks with dangerous weight loss pills. BoJack lands the title role on Philbert, an original detective web-series that streams on WhatTimeIsItRightNow.com.

In season 5, while working on Philbert, BoJack begins dating co-star Gina Cazador. During the show's production, he suffers an on-set accident and develops an addiction to prescription painkillers. The first season of Philbert becomes a huge success, and production of season 2 begins almost immediately; during this time, however, BoJack's drug problem worsens until one day on set, while heavily under the influence of painkillers (and likely Philbert-based schizophrenia), he chokes Gina and forgets shortly after.^[9] Despite Gina not pressing charges and still working with him, she cuts off personal ties with BoJack before their cover-up interview with Biscuits Braxby. Season 5 ends with Philbert getting cancelled due to Todd's robot CEO facing sexual allegations, and BoJack checking himself into rehab with Diane's transport and urging.

Season 6

In the first half of season 6, he is seen as having been healed significantly as a result of rehab. In the season six episode "The Face of Depression", it is revealed he's been coloring his hair black for the last 20 years; the real color of his hair is grey.^[10] At the end of this episode, BoJack accepts a role as a drama teacher at Wesleyan University, where Hollyhock is a student, after Raven-Symoné removes herself from consideration.^[11] He enjoys this new job and quieter life, forging a deep connection with his students and discovering a newfound love of teaching, though he struggles to connect with Hollyhock, whom over winter break learned about him intoxicating Maddy and silencing Pete in New Mexico, though she does not directly confront him on this. In the second half of season 6, after a student actor showcase with Diane, Princess Carolyn, and Todd in attendance, BoJack receives a call from Charlotte telling him that reporters have been pestering her in her home for information about his time in New Mexico and orders him to get rid of them; this gives BoJack an anxiety attack and causes him to come to terms with the fact that details of his past are about to come to light. The following week, the Hollywoo Reporter publishes an article providing all the details of Sarah Lynn's death, revealing to the public for the first time BoJack's involvement in it.

BoJack attempts to capitalize on the upcoming interview regarding his role in Sarah Lynn's death. While initially receiving praise for his honesty, he is effectively "canceled" after the second interview uncovers his influential erratic relationships with women in his circle, and his true culpability: by him waiting 17 minutes to call the ambulance, Sarah Lynn actually died at the hospital. BoJack hits rock-bottom, losing his teaching job, his house, and his relationship with Hollyhock, and is blackballed in Hollywood. He forms an unlikely friendship with fellow "canceled" actor Vance Waggoner, who encourages him to channel his anger into work, their first being a bawdy, low-brow comedy film called The Horny Unicorn. BoJack is eventually contacted by Angela Diaz, the network executive who in the '90s intimidated him into keeping quiet about Herb's outing. She tells BoJack that the network is releasing new versions of Horsin' Around with all his scenes cut, and goads him to take up drinking again after signing away his residual credit. BoJack gets drunk with her and learns that Angela manipulated him into allowing Herb's firing. When she rejects his condemnation and retorts they were equally opportunistic, BoJack gives into his despair, breaking into his old home and reverting to his old habits. After attempting to contact Diane with a casually desperate voice mail, BoJack attempts suicide by overdosing on pills and drowning in his old swimming pool, experiencing a near-death experience in which he faces the options of his shattered life through the visions and stories of his deceased family and associates, hosted by Herb himself. He ultimately ends the vision in a conversation with a distal version of Diane over the Horsin' set phone as black tar swallows him.