Professor Kenzou Mukai
An old man dedicated to the pursuit of justice. He worked as a mentor for the B-Fighters, usually working at Earth Academia to assist the team by leading research on Jamahl's warriors and developing new weaponry and vehicles for the B-Fighters. He fell in love with Sayuri, a plant researcher, many years ago, but left her. When they met once again during Rasbelga's attack, Mukai donned a special armor and donned the title of "Mukaider K3" to save her.

Mukaider K3

Insect Elder Guru
The elder of the insect tribe, and looks like a giant yellow rhinobeetle. He carries a staff with a curled top. Guru possesses great the mystical power of his own. Takuya bumped into him inside of a cave, when he appeared to him. He gave the B-Fighters their powers.

Muscle was a mysterious armored amphibious alien who arrives on Earth with a shining feather that belongs to Saint Papilia. He was once healed by her power, and had followed clues about her to Earth. Muscle was defeated and Black Beet gained possession of Papilia's feather. He appeared in Episode 40.

Saint Papilia
A legendary 'butterfly of life' who can grant immortality. She appears when the life on a world has been diminished. She then revives the world by giving it new life. Saint Papilia already appeared once on Earth, after the Ice Age, and revived the Earth so the life of today could be born and grow. Saint Papilia has also revived Muscle during the course of her existence. Both Gaohm and Black Beet sought Saint Papilia in the hopes of obtaining her gift of eternal life. After Takuya defeated Shadow, he was severely wounded and died. Saint Papilia appeared above him and resurrected him, saying that Earth still needed him.

Drago is another insect warrior and his powers are dragonfly based. Battling with Blue Beet restores the memory of his past he has lost. Once learning who he really was, he helped the B-Fighters defeat Hells Gyra.

A scientist from the Aroa dimension who falls in love with Takuya.

A ghost called forth by one of Jera's soldiers who breaks free of his control and helps fight against him.

A contestant in Jamahl's "Ghost Zone" battle that Jamahl had, for which they kidnapped the B-Fighters, which sent them another dimension, and forced them to participate in combat. Daisaku soon learned that Sinbad was infiltrating Jamahl in an attempt to assassinate Gaohm for destroying his homeworld. Gaohm learned of this, however, and sent a resurrected Death Mult to kill Sinbad and the B-Fighters. Realizing that the only way for the B-Fighters to return home was by the explosion caused by Death Mult's demise, Sinbad kamikazed Death Mult and killed them both. Before the B-Fighters became free and left the dimension, Sinbad asked them to please defeat Gaohm and the Jamahl.

Tokusou Robo Janperson and Gun Gibson
The robotic detective heroes from their respective Metal Heroes series Tokusou Robo Janperson, they appeared and assisted the B-Fighters in their battle against Jagul at the end of the series.

Shou, Sig and Sarah (Blue SWAT, Grey SWAT, Purple SWAT)
Trio of special, heavily armed alien-destroying heroes from the Metal Heroes series Blue SWAT. Sarah and Mai were captured by Jagul, and Shou and Sig, along with Janperson and Gun Gibson, aided the B-Fighters to rescue them.

B-Fighter Kabuto
The next generation of B-Fighters 10 years later. The original B-Fighter go to assist them in the search for eight powerful medals but are infected by a virus that makes them fight each other. When the virus is frozen, they able to overcome it.