Characters

• Kanzo Hattori (ハットリ カンゾウ or 服部 貫蔵 Hattori Kanzou^?) (voice: Junko Hori, drama actor: Kōtoku Nomura, drama voice: Kazuo Imakura, live-action film actor: Shingo Katori), aka Hattori-kun, is the protagonist of the series, a little ninja. He is 11 years old and 40 kg and is 140 cm tall. He is the boy who usually contests Kemumaki when he performs mischief. Hattori's main weakness is that he is afraid of frogs; this often leads him into trouble and becomes helpless. He wears blue coloured ninja robes. He always explains what a good ninja does and what others should also do. His powers can be compared to a master ninja. He also has a strange habit of saying ~degozaru or nin nin after almost every sentence. His girlfriend seems to be Tsubame.

• Shinzo Hattori (ハットリ シンゾウ or 服部 心蔵 Hattori Shinzou^?) (voice: Yūko Mita, drama actor: Shigeki Nakajō), aka Shin-chan, is Kanzo's younger brother. A good point to note is that while Kanzo is referred to as "Hattori", Shinzo is usually called by his first name. He uses weapons made from wood. He is a ninja-in-training who learns to be a good ninja, like Kanzo. He wears red coloured ninja robes. Shinzo seems to have a good heart and sticks to being loyal to his brother and sometimes gets excited when others are excited. Some of the times, Shinzo tricks Hattori to giving him things. He is also known to cry very loudly, which makes people faint. He is also very powerful for his age. He helps Kanzo fight Kemumaki, with his real weapons and control his loud crying (Which immobilizes opponents from attacking) and bites the head of the opponents.

• Shishimaru (獅子丸^?) (voiced by Kenichi Ogata) is a ninja dog living with Ken'ichi, who came along with Kanzo Hattori and Shinzo Hattori. He is a casual behaving dog who at times becomes lazy and stubborn. Along with Shinzo,the two of them wind up doing mischief and creating trouble. He has an attack of turning in a fireball when provoked. He also has the ability to change form into any other animal. His fur color is yellow. His ninja mark on his forehead is very important for him as its an identification of him as a ninja. He loves to eat all kinds of delicious treats, especially chocolate roll.

• Kenichi Mitsuba (三葉 ケン一 Mitsuba Kenichi^?) (voice: Masako Sugaya, drama actor: Katsumi Takamiya, live-action film actor: Yuri Chinen) is a 10-year-old boy who goes to middle school and is poor in his studies. He likes Yumeko, however also Kemumaki is always after her. He also tricks Hattori to help him in any situation. He also does not follow his mother's instructions properly and often gets a severe scolding from his mother.Though he doesn't study well,he has a good habit of helping others. He is always the victim of Kemumaki's mischievous plans.

• Tsubame (voice: Fuyumi Shiraishi), aka Tsubame-ko, a kunoichi and classmate of Hattori-kun. She likes Hattori and always wishes to marry him. She has a dislike for Kemumaki and Kagekiyo. She wears pink coloured ninja robes. She seems to own a recorder, a clarinet, a flute, a piccolo and a bassoon, five woodwind instruments. She is called as 'Sonam' in the Hindi version.

• Kemuzo Kemumaki (ケムマキ・ケムゾウ Kemumaki Kemuzou^?) (voice: Kaneta Kimotsuki, live-action film actor: Gorie) is the antagonist of Ninja Hattori-kun. He, along with his cat Kagechiyo Kemuzou, always are the ones who cause trouble. Strength-wise, he has competition with Hattori and Shinzo. He is 11 years old and is shorter than Ken'ichi but a lot more fitter and stronger than him. He competes with Ken'ichi for Yumeko-chan; however when he uses one of his ninja techniques in order to win, Hattori usually steps in to save the day. He wears green colored ninja robes. Only Kagechiyo, Kenichi and the Kanzo family know about his duel life that he's a ninja like Hattori while he joined Kenichi's school as a normal boy in the middle of the series. His parents' whereabouts are unknown, but his mother is noted several times in the series. He is called as 'Amara' in the Hindi version.

• Keiyo (影千代^?) (voice: Eiko Yamada, is a talking animal-ninja of the Koga-ryu, Kagechiyo is the helping antagonist of Ninja Hattori. Usually Kemumaki gives a big task in his plans for Kagechiyo to carry out, but he fails it. This is because he doesn't get enough training from Kemumaki and is seen sleeping on the streets. He is noticed by Hattori several times. He is seen to have an enmity of Shishimaru. His fur color is black. He normally hides in the Mitsuba house to hear Kenichi and his friends' plans and afterwards informs Kemumaki about them, acting more like a communication device. Sometimes he hates Kemumaki for his strictness and imagines living a life of luxury as a normal cat in some episodes. He enjoys eating fish. He obtains an attack of static electricity on rubbing a shining metal plate against his back. If he uses this attack too much then he feels weak. He is called as 'Kiyo'in the Indian version.

• Yumako Kawai (河合 夢子 Kawai Yumeko^?) (voice: Runa Akiyama), aka Yumeko-chan, is the girl who usually causes disputes between Kemumaki Kemuzou and Ken'ichi Mitsuba. She also attends the same middle school as the two, and she is also the one who causes most of the problems of the plot. Most of the time she appears to be confused. Yumeko seems to be in touch with Hattori sometimes. Yumeko sees Hattori as a big brother and Shinzo as a little brother. She is also seen to like Kenichi. And sometimes people mistake her relationship with Hattori as a romantic one, though in some episodes they are seen to show romance. In Race-Tin: Flash and Dash Unleashed she is the antagonist, and loves to cause trouble.

• Aiko-Ma'am (voice: Yōko Kawanami):One of Ken'ichi's teacher. Koike-sensei has a crush on her. The subject she teaches is unknown.
• Hattori Jinchuu (voice: Tadao Futami): Hattori-kun and Shinzo's father.
• Jippou (voice: Junpei Takiguchi, drama voice: Hiroko Maruyama): A giant turtle monster ninja.He and Hattori are ninja partners.
• Koike-Sir (voice: Issei Futamata): Ken'ichi's teacher, also appears as a ramen chef in Obake no Q-tarō and sometimes appear as a cameo in Doraemon where he eats ramen. He always scolds Kenichi similar to when Nobita is scolded by his teacher in Doraemon. He is caricatured after animator Shin'ichi Suzuki. He also appears in the cartoon "Biriken" and "Ultra B" as Michio's father.
• Kentaru Mitsuba (voice: Yuzuru Fujimoto, drama actor: Teizō Muta): Kenichi's father. He usually smokes and comes from his office late in the evening. He likes eating and golf a lot.
• Amma (voice: Yuri Nishiwa, drama actor: Chiharu Kuri): The mother of Kenichi. She likes Tsubame and thinks that Kemumaki is a good boy.
• Professor Shinobino (voice: Reizō Nomoto): A professor who lives in America and invented Togejirou
• Cacto-Chan (voice: Hiroko Maruyama): A cactus having supernatural powers is sent by Professor Shinobino from America. Shisimaru does not like Togejirou and loves to compete with him. In the English and Hindi version, he is called Cactochan (Kak-toe-Chan).