The various characters in the series include but are not limited to:
- Jō Yabuki (矢吹 丈 Yabuki Jō), nickname is Joe (ジョー Jō)
- Voiced by: Teruhiko Aoi, Kei Tomiyama (Pilot Film), Yoshito Yasuhara (Radio Drama)
- Live-Action Film: Shōji Ishibashi (1970), Tomohisa Yamashita (2011)
- Italian Name: Rocky Joe
The protagonist of the story. An OPBF Champion and 1st in the World Ranking. He is known for his long bangs and for always wearing a worn out beige coat and a red flat cap. Not long after birth he found himself in many orphanages and facilities. However, he quickly grew tired of the boring life and frequently escaped in search for 'a place of happiness' (or as Danpei Tange refers to it as 'tomorrow'), eventually finding his way to the Doya Town, where the story takes place. In the last moments of the story his smile indicates that he finds his 'place of happiness' i.e. boxing.
Joe is rude and quick to fight, but he can also be very frivolous at times. Because of his rough upbringing he is a delinquent who likes his solitude, but he later grows to appreciate his new friends and rivals. He is not very good at understanding women, and essentially only treats them nice out of giri. Usually when the situations become emotional he likes to act tough to avoid people from finding his soft side. As a result of Riki'ishi's death, he temporarily suffers from yips and cannot hit people in the temple, but he later overcomes this. This allows him to move past the loss of Riki'ishi. He often feels really hurt when he finds out that something bad has happened to his opponents due to their match.
He is a bantamweight and his specialties include the cross counter and the No Guard stance. He has extraordinary punching strength, fortitude, and boxing spirit, often standing up after taking killer blows and has been known to counter cross-counters (a double-cross), possessing a raw, natural talent for the sport. He has even countered double crosses with a triple-cross, implying he has high-level technical abilities. Following his fight with Riki'ishi, he begins to better develop his guarding. During his fight with Jos'e, he even unconsciously uses his own corkscrew punch against Jos'e.
- Danpei Tange (丹下 段平 Tange Danpei )
- Voiced by: Jūkei Fujioka, Takeshi Aono (Boxing Mania Video Game), Akira Nagoya (Pilot Film), Haruhiko Saitō (Radio Drama)
- Live-Action Film: Ryūtarō Tatsumi (1970), Teruyuki Kagawa (2011)
- He is an ex-boxer who was unable to fulfil his dream of becoming the world champion (most probably because of losing his eye). Due to his broken dreams he tries to become boxing coach of the boxer who could become the world champion but all his students abandon him. As a result of this he starts drinking to forget the pain of his broken dreams but one day he finds a boy capable of becoming a world champion, Joe Yabuki. I.e He believes that Joe has a bright 'tomorrow'. Danpei tries to convince him to become a boxer but it goes in vain till Joe himself finds a reason to box.
- After Joe comes back to Namida bridge from the correction house. Danpei starts training him for becoming a professional boxer. Initially, Danpei looks at Joe as a means to fulfil his Dreams, but later he truly starts caring for Joe.
- Mammoth Nishi (マンモス西)
- Voiced by: Toku Nishio, Jiro Daruma (Ashita no Joe 2), Shiro Kishibe (Film), Daisuke Gōri (Boxing Mania Video Game)
- Live-Action Film: Masaaki Yamamoto (1970), Katsuya (2011)
- Real name Kanichi Nishi (西 寛一 Nishi Kanichi )
- Nishi is Joe's best friend, sparring partner and later he also becomes Joe's trainer. He is a juvenile delinquent. He first meets Joe in a juvenile jail, where they fight each other and Joe defeats him. Nishi later meets Joe at the correction house where they become friends.
- Nishi's personality changes drastically from an arrogant juvenile delinquent to calm worker at a grocery store. He takes a liking to boxing after watching Joe's match against Rikishi. When Joe comes back to Namida Bridge he is surprised to find Nishi at the Tange boxing gym, Nishi joins the gym to learn boxing and to continue being with Joe. Nishi is an averagely good boxer. He was the only useful sparring partner Joe had in the entire story. Nishi has a crush on Noriko Hayashi, who is the daughter of his boss at the grocery store. Nishi injures his fist in a match and painfully decides to retire from boxing. In his retirement party he confesses that he will always be proud of dedicating his youth to boxing. Later, Nishi marries Noriko and becomes more dedicated to his work at the convenience store but he also continues to help Joe with his training.
- Yōko Shiraki (Shiraki Yōko)
- Voiced by: Kazuko Nishizawa, Masako Ebisu (ep. 34~44), Emi Tanaka (Ashita no Joe 2), Fumi Dan (Film)
- Live-Action Film: Yōko Takagi (1970), Karina (2011)
- Tohru Rikiishi (力石 徹 Rikiishi Tōru )
- Voiced by: Shūsei Nakamura, Toshiyuki Hosokawa (Film), Hideyuki Hori (Boxing Mania Video Game), Kōji Shimizu (Radio Drama)
- Live-Action Film: Seiichirō Kameishi (1970), Yūsuke Iseya (2011)
- Italian Name: Toro Riki
- Mikinosuke Shiraki (白木 幹之介 Shiraki Mikinosuke )
- Voiced by: Tamio Ōki
- Live-Action Film: Bontarō Miake (1970), Masahiko Tsugawa (2011)
- Wolf Kanagushi (ウルフ金串 Urufu Kanagushi )
- Voiced by: Osamu Katō, Gorō Naya (Ashita no Joe 2)
- Live-Action Film: Speedy Hayase (1970), Mitsuki Koga (2011)
- Jun Shioya (塩谷ジュン Shioya Jun )
- Voiced by: Keiko Yokozawa (Ashita no Joe 2)
- Wolf's fiancée.
- Jiro Shioya (塩谷ジロー Shioya Jirō )
- Voiced by: Yoku Shioya (Ashita no Joe 2)
Jun's little brother. He is on the verge of becoming a juvenile delinquent but after a little bit of encouragement by the OPBF champion, Joe Yabuki, he decides to learn boxing seriously and sells away his bike.
- Carlos Rivera (カーロス・リベラ)
- Voiced by: Taichirō Hirokawa, Ryūsei Nakao (Ashita no Joe 2), Joe Yamanaka (Film)
- Harry Robert (ハリー・ロバート)
- Voiced by: Takeshi Kuwabara, Michihiro Ikemizu (Ashita no Joe 2)
- Carlos Rivera's manager & childhood bestfriend.
- Kim Yongpi (金 竜飛 Kin Ryūhi )
- Voiced by: Norio Wakamoto (Ashita no Joe 2)
- Harimau (ハリマオ Harimao )
- Voiced by: Takashi Taguchi (Ashita no Joe 2)
- Italian Name: Hamario
- Kinoko (キノコ Mushroom )
- Voiced by: Keiko Ushizaki, Junko Hori (Ashita no Joe 2)
- Hyoromatsu (ヒョロ松)
- Voiced by: Kaneta Kimotsuki
- Chūkichi (チュー吉)
- Voiced by: Noriko Tsukase
- Tonkichi (トン吉)
- Voiced by: Jōji Yanami, Hiroko Maruyama (Ashita no Joe 2)
- Chibi (チビ Squirt )
- Voiced by: Mitsuko Asō
- Noriko Hayashi (林 紀子 Hayashi Noriko )
- Voiced by: Kaoru Ozawa, Kei Moriwaki (Ashita no Joe 2)
- Keishichi Hayashi (林 敬七 Hayashi Keishichi )
- Voiced by: Setsuo Wakui, Minoru Yada (Ashita no Joe 2)
- Tamako Hayashi (林 玉子 Hayashi Tamako )
- Voiced by: Teruko Abe, Shō Saitō (Ashita no Joe 2)